Tag: Tort Law

 

Torts and Restitution: Legal Divergence and Economic Convergence

Robert Cooter[*] & Ariel Porat[†]

This Article explores the divergence in law and convergence in economics in dealing with harms and benefits. While tort law usually makes the injurer internalize wrongful harms through damages, restitution law does not enable the benefactor to internalize the benefits she confers on others without their request. In both harm and benefit cases, however, internalization seems to make economic sense for the same reason: injurers and benefactors alike will behave efficiently if they internalize the externalities that they create. The Article’s main goal is to develop eight liability rules for harm and benefit cases and to point out the symmetry between the rules relating to harms and the rules relating to benefits. It also provides an explanation for the legal divergence between tort law and restitution law and makes the claim that the gap between these two fields should be narrowed. Finally, the Article relates these eight rules to the main relevant categories of harm and benefit cases in positive law and appraises their advantages and disadvantages.

Introduction

Tort law usually makes the injurer internalize wrongful harms through damages. In contrast, restitution law does not enable the benefactor to internalize the benefits she confers on others without their request, through damages, and only seldom allows her to recover the costs she incurs in creating those benefits. Thus, law is divergent in dealing with harms and benefits. In both kinds of cases, however, internalization seems to make economic sense for the same reason: injurers and benefactors alike will behave efficiently if they internalize the externalities that they create.[1] Since the economics is convergent, why is the law divergent? Can efficiency explain the law’s divergent treatment of harms and benefits?[2]

This Article provides a detailed analysis of economic convergence in actual and possible rules of torts and restitution. A better understanding of economic convergence will lead to better understanding of legal divergence, as well as a critique of it. We will argue that legal divergence mostly makes sense, but a modest expansion in restitution’s scope, which would increase convergence, would also increase efficiency.

In Part I we develop eight liability rules for harm and benefit cases and point out the symmetry between the rules relating to harms and the rules relating to benefits. Part II presents and discusses the divergence of tort and restitution laws and provides an explanation for this divergence. It makes the claim that the gap between the two fields should be narrowed. Part III relates the eight rules developed in Part I to the main relevant categories of cases in positive law and appraises their advantages and disadvantages.

I.  Liability Rules for Harms and Benefits

In this Part we discuss and develop eight liability rules—half for harm cases and half for benefit cases. We start by presenting the eight rules by using two examples.

A.  Introducing the Rules

Consider the following cases:

Example 1: Omitting a Test. Doctor in a public hospital performs a beneficial procedure for a patient. In addition to the benefit, the procedure causes harmful side effects of 100. A test that costs Doctor 20 can prevent the harmful side effects. Doctor omits the test and the harm materializes.

Example 2: Constructing a Garden. Builder considers constructing a garden on her land that will increase the market value of her house and five Neighbors’ houses. The garden costs Builder 15. The increase in the value of Builder’s house is 10, and the increase in the value of each Neighbor’s house is 2.[3] The benefits are a public good: Builder cannot prevent Neighbors from enjoying the garden’s benefits once it is created. Since each Neighbor knows that their own benefit from the public good does not depend on their contribution to its costs, they contribute nothing, hoping that Builder and the other Neighbors will pay for the garden. However, since all Neighbors reason in the same way, nobody pays. Nevertheless, Builder constructs the garden, conferring a total benefit to Neighbors of 10.

In both harm and benefit cases the law could make the actor—the injurer or the benefactor—internalize the externalities she creates. One possibility for the law is to make internalization unconditional on the behavior of the actor. In Example 1, unconditional internalization is a rule of strict liability for harm with compensatory damages (Rule H1). Under this rule Doctor is liable for the harm she causes, at the amount of that harm, regardless of whether she behaves negligently. Thus, even if the costs of administering the test were higher than expected harm and therefore there was no negligence on Doctor’s part,[4] Doctor would bear liability for the harm caused to the patient. In Example 2, unconditional internalization is a rule of strict restitution for benefit with disgorgement damages (Rule B1). Under this rule Builder is entitled to restitution at the amount of the benefit she confers, regardless of whether she behaves reasonably. Thus, even if the costs of constructing the garden were higher than expected benefit, Builder would be entitled to disgorgement damages from Neighbors.

Another possibility is to condition internalization on whether the behavior of the actor is reasonable or not. In harm cases, this is a rule of negligent liability for harm with compensatory damages (Rule H3). According to this rule, in Example 1, Doctor will be liable for the harm she causes, at the amount of that harm, only if she is negligent, namely, only if her costs of care are lower than expected harm.[5] In benefit cases, this is a rule of reasonable restitution for benefit with disgorgement damages (Rule B3). According to this rule, in Example 2, Builder will be entitled to damages at the amount of the benefits she confers, only if she behaves reasonably, namely, only if her costs of constructing the garden are lower than expected benefit.

To summarize, under the four rules discussed so far, both negative and positive externalities are internalized by their creators. While under the first two rules (H1 and B1) internalization is unconditional on the character of the creator’s behavior, under the other two rules (H3 and B3) internalization is conditional on the reasonableness of her behavior (under Rule H3 unreasonableness entails internalization, while under Rule B3 reasonableness entails internalization).

Instead of internalization, the law could aim to deter injurers from causing harms or encourage benefactors to confer benefits by removing their incentives to cause harms or not to confer benefits. In harm cases, the law could make the injurer disgorge her benefits from creating risks, thereby deterring her from engaging in such a behavior. It could be unconditional on the injurer’s negligence (Rule H2) or conditional upon it (Rule H4). The first rule (H2) is strict liability for harm with disgorgement damages: damages are not at the amount of the harm caused but rather at the amount of the injurer’s benefits from engaging in the risky behavior. The second rule (H4) is negligent liability for harm with disgorgement damages: damages are at the amount of the injurer’s benefit from engaging in the negligent behavior. Thus, in Example 1, under both Rules H2 and H4, Doctor’s liability is at the amount of 20, rather than 100.

In benefit cases, there are parallels to Rules H2 and H4. Thus, the law could make the benefactor entitled to damages at the amount of her costs in creating the benefits, thereby encouraging her to confer them, either unconditional (Rule B2) or conditional on her behavior being reasonable (Rule B4). Rule B2 is strict restitution for benefit with compensatory damages, and Rule B4 is reasonable restitution for benefit with compensatory damages. Thus, in Example 2, under both Rules B2 and B4, Builder is entitled to damages at the amount of 7.5 from Neighbors (1.5 from each), which is their relative share in the costs incurred by Builder.

The table below summarizes the eight liability rules (marking with an asterisk (*) those rules which currently exist under the law). The next Section analyzes the eight rules in more detail.

B.  Strict Liability and Internalization (Rules H1 and B1)

Under a rule of strict liability for harm with compensatory damages (Rule H1), the injurer is liable whenever his activity causes an accident, regardless of his level of care. Strict liability with perfectly compensatory damages causes the injurer to internalize the harm from accidents that he causes to victims. Consequently, the self-interested injurer has an incentive to take socially efficient precautions and maintain a reasonable activity level.[6] Conversely, under this rule, the victim externalizes the effects of her precautions and activity level. Consequently, the victim has no incentive to take precaution or restrain her activity levels. The victim’s precaution is deficient and her activity is excessive relative to the social optimum. To illustrate, with strict liability with perfect compensatory damages, drivers take efficient precautions (for example, installing cost-justified safety devices in their cars) and their activity level is efficient (for example, driving at efficient frequency). Pedestrians, however, as potential victims, have no incentives to take precautions or restrain their activity, because they are fully compensated.[7]

Now we turn from torts to the equivalent analysis of restitution. Strict liability for harm with compensatory damages (Rule H1) corresponds to strict restitution for benefit with disgorgement damages (Rule B1). Disgorgement by the beneficiary causes the benefactor to internalize the effects on the beneficiary. Consequently, the benefactor has an incentive for the socially efficient benefaction. As in the standard tort model, internalization by one party causes externalization by the other, so Rule B1 makes the beneficiary externalize the value of the gains from the benefaction. Consequently, the beneficiary has no incentive to increase the benefaction’s value. The beneficiary’s activities are deficient relative to the social optimum.[8]

To illustrate by Example 2, under Rule B1, Builder has efficient incentives to construct the garden in the most efficient way (for example, using adequate materials and labor). Also, her ancillary activity (or activity level)—which is mostly relevant if Builder is in the business of constructing gardens—will be efficient (for example, investing in finding adequate places for gardens). At the same time, however, Neighbors lack incentives to take steps that increase the value which they might derive from the garden (for example, by constructing the windows of their homes to face the garden), since the entire value would be disgorged to Builder.[9]

C.  Strict Liability and Deterrence or Encouragement (Rules H2 and B2)

Now we turn from internalizing harms and benefits to deterring harms and encouraging benefits. First, consider a rule of strict liability for harm with disgorgement damages (Rule H2). Disgorgement damages under this rule make the injurer give up his gain from imposing risk on the victim. If the injurer does not expect to gain by imposing risk on the victim, he might as well not impose any. Consequently, disgorgement damages are the minimum damages that deter the injurer from imposing the risk of an accident on the victim. However, efficiency usually requires the injurer to impose some risk on the victim, in which case damages are inefficient—they cause excessive precaution or deficient activity by the injurer. Also, with Rule H2, victims have deficient incentives for precaution and their activity is excessive compared to the social optimum because injurers do not impose any risks on them. To illustrate with Example 1, suppose the test necessary to prevent the side effects to the patient cost Doctor 200 rather than 20. Under Rule H2, Doctor would administer the test—although efficiency-wise, she should not—because not administering the test would cost her 200.[10]

Equivalently, consider the rule of strict restitution for benefits with compensatory damages (B2). Compensatory damages for unrequested benefits are the minimum damages that encourage the benefactor to maximize benefits to the beneficiary. When damages are perfectly compensatory, they exactly offset the benefactor’s cost of supplying an unrequested benefit. Since the benefactor expects to bear no net cost from creating benefits for the beneficiary, the benefactor will maximize the benefaction without regard to the cost of doing so.[11] This inefficiency, however, might disappear if the benefactor creates at the same time benefits for herself and for others and is entitled only to the relative share of her costs proportionate to the benefits she confers on others. To illustrate with Example 2, under Rule B2, Builder would not invest excessively in constructing the garden because Neighbors compensate her for only a relative share of her costs, so that Builder bears the rest of it.[12]

Besides the benefaction, the benefactor’s ancillary activities may increase the benefits to others without increasing her compensatory damages. Consequently, the benefactor’s ancillary activity level will be deficient.[13] As to the beneficiary, his incentives would be efficient because he internalizes the benefits he creates.

D.  Negligent Liability and Internalization (Rules H3 and B3)

Now we turn from strict liability to negligence, beginning with negligent liability for harm with compensatory damages (Rule H3). The incentive effects of a rule of negligence with compensatory damages are well known in torts literature. In the basic model, a negligence rule causes the injurer to avoid liability by satisfying the legal standard, which is assumed to be the efficient level of care. Having escaped liability, the injurer has no incentive to restrain his activity level. When the injurer escapes liability, the victim internalizes the harm from accidents, so she has incentives for socially efficient precaution and activity.[14]

The equivalent rule is reasonable restitution for benefits with disgorgement damages (B3). Under this rule, the benefactor enjoys restitution for her benefaction up to the legal standard, which is assumed to be efficient, and no restitution for additional benefaction beyond it. Therefore, the benefactor satisfies the legal standard and her benefaction is at the socially efficient level. Since she internalizes all the benefits she reasonably creates, her ancillary activity is also efficient. However, the beneficiary, on his part, has no incentives to increase the value produced by the benefactor since he disgorges any value he gains from reasonable benefaction.[15] To illustrate with Example 2, under Rule B3, Builder invests efficiently in constructing the garden and Neighbors have no incentives to increase its value even if they can do so.

E.  Negligent Liability and Deterrence or Encouragement (Rules H4 and B4)

We conclude the analysis of negligent liability by considering damages that deter or encourage reasonable behavior, instead of internalizing it. Instead of compensation, consider disgorgement for unreasonable harms. Under a negligence rule, disgorgement damages make the injurer give up his expected gain from imposing unreasonable risk on the victim. This can be accomplished if damages amount to the savings in untaken precautions. Since the injurer does not expect to gain by imposing unreasonable risk on the victim, he might as well take reasonable care. Consequently, a rule of negligence for harm with disgorgement damages (Rule H4) causes efficient care by the injurer. To illustrate, in Example 1, Doctor’s liability is 20, and this amount (plus epsilon) is enough to deter her from negligently omitting the test for the patient. The injurer’s activity level, however, is excessive,[16] while the victim’s incentives and activity levels are efficient.[17]

Now consider the equivalent rule of restitution, which is reasonable restitution for benefit with compensatory damages (Rule B4). Under this rule, the benefactor is compensated for the cost of conveying unrequested benefits to the beneficiary that are reasonable. So long as the benefaction is reasonable, damages exactly offset the benefactor’s cost of supplying unrequested benefits. Since the benefactor expects to bear no net cost from creating benefits for the beneficiary up to the reasonable level, he might as well supply the reasonable level of benefits.

The rule of reasonable restitution with compensatory damages creates incentives for efficient benefaction. Although the benefactor receives compensatory damages for the benefaction, the benefactor receives no damages for ancillary activities that increase its value to the beneficiary, so he has socially deficient incentives for ancillary activities. The beneficiary, however, internalizes the benefits from her activities, so she has incentives for socially efficient activities.

F.  Summary

Table 2 summarizes the incentive effects of all eight liability rules. The rules are arranged to show the symmetry between liability for harm and for benefits. As the table shows, the symmetry is not perfect, especially when it comes to Rules H3 (negligent liability for harm with compensatory damages) and B3 (reasonable restitution for benefits with disgorgement damages).

The efficiency of the different rules depends crucially on the information available to the parties involved, as well as to courts applying the different rules. Because of space constraints we cannot analyze the informational hurdles systematically. Instead, we refer to them sporadically in the next Parts of this Article, whenever necessary.
II.  Torts and Restitution—A Convergence?

Having explained economic convergence in harms and benefits, we will now explain legal divergence. With zero transaction costs, legal rules do not affect efficiency, as explained by Professor Ronald Coase.[18] With few parties, however, transaction costs are typically low but not zero. When transaction costs are low, the law often encourages the parties to negotiate a contract rather than act unilaterally. In harm cases with two pre-identified parties, as in conversion and trespass cases, the injurer is not allowed to act unilaterally against the victim and pay for the harm done. Instead, the law deters the harm, notably through injunctions against trespass or conversion and disgorgement of benefits,[19] thereby channeling the parties into negotiations. The same is true with benefits. The benefactor is not allowed to paint the beneficiary’s fence and charge her accordingly. Instead, the law deters the benefactor from conferring the unrequested benefit by denying him any recovery, thereby channeling the parties into negotiations.[20]

Whereas the legal rule is symmetrical with respect to harm and benefits in these low transaction cost cases, it is asymmetrical in high transaction cost cases. Assume that high transaction costs preclude market transactions in harm and benefit cases, so the law cannot successfully channel the parties to negotiate. Without negotiations, it seems that injurers and benefactors alike should be allowed to act unilaterally, and the law should make them internalize the consequences or else deter them from behaving inefficiently (in harm cases) or encourage them to behave efficiently (in benefit cases). In fact, however, the law allows the unilateral imposition of harms and often requires internalization by the injurer, whereas the law allows the unilateral conferral of benefits, but does not require internalization by the benefactor, and seldom requires reimbursing her costs.[21]

Can efficiency explain the law’s divergent treatment of harms and benefits?[22] One possible reason could be difficulties in measuring benefits. Thus, in harm cases the plaintiff-victim possesses information about the negative externalities (the harms), while in benefit cases the defendant-beneficiary possesses information about the positive externalities (the benefits). Perhaps courts can measure the former easier than the latter so that courts allow recovery more readily for harms than for benefits.[23]

This argument, however, cannot survive scrutiny. Calculating the harm to the victim of an injury is not systematically easier for the court than calculating the benefit to the beneficiary. Differences in the difficulty of measuring damages seem too random and small to explain systematic and large differences in the scope of liability for harms and benefits.[24]

A more plausible reason for the systematic legal differences is enforcement and litigation costs. If the legal rule for harms is negligence then most injurers do not behave negligently, so few victims can claim damages.[25] In contrast, if the legal rule for benefits is strict restitution or reasonable restitution, many benefactors can claim damages. Thus, we expect many claims by benefactors in the few types of cases where restitution law allows recovery.[26] Perhaps restitution law restricts recovery to a few types of cases in order to avoid a flood of claims.

This explanation of the difference between harm and benefit cases works best when small and unequal benefits accrue to many beneficiaries. However, this difference cannot explain the large asymmetry between torts and restitution. It works poorly when uniformly high benefits accrue to a small group of well-defined beneficiaries.[27] Also, the assertion that harms induce fewer claims applies to a negligence rule but not to a rule of strict liability where many victims of harm can claim damages.[28]

The next reason, in our view, is convincing and more complete. It concerns the difference in costs of market transactions in harm and benefit cases. In a typical harm case with high transaction costs, there is one injurer and many victims. If the law prevents injurers from acting unilaterally without first obtaining consent from the victims, each victim will have veto power over the risky activity. Each victim has an incentive to hold out for a high payment as a condition for consenting. Thus, holdouts will block many socially efficient activities that risk harm to multiple victims.[29] Therefore, the law allows injurers to act unilaterally. However, it also forces them to compensate the victims for the resulting harm or wrongful harm. With permission to act unilaterally, but with no duty to compensate, injurers would not restrain their injurious activities.[30]

Switching from harms to benefits, in a typical benefit case with high transaction costs, there is one benefactor and many beneficiaries. If the law allows the benefactor to act unilaterally without requiring the beneficiaries to pay damages to the benefactor, each beneficiary will have an incentive to free ride on the contributions of others. The free-riding problem will reduce the supply of benefits but not block them.[31] To illustrate, in cases represented by Example 2 (Constructing a Garden), if three out of the five neighbors would share in the costs of construction, even with no liability imposed on the other two (free-riding) neighbors, the garden might be constructed.

As explained, the typical transaction costs in harm cases are holdout, while the typical transaction costs in benefit cases are free riding. Free riding on benefits is less socially destructive than holding out consent to risky activities. The greater legal scope of liability for harms relative to liability for benefits is explained by the greater destructiveness of withholding consent to risky activities compared to free riding on benefits. This fact could provide an explanation for why there are broad rights in the law for the unilateral creation of harms coupled with their internalization and broad rights for the unilateral creation of benefits but only rarely coupled with liability on the part of the beneficiaries.

In our view, however, the law would better promote social welfare with a broader liability for unrequested benefits. In Part I we explained how different liability rules could be applied to harm and benefit cases. In the next Part we apply those rules to the main categories of cases of torts and restitution and show how, by allowing broader liability for unrequested benefits, the asymmetry between torts and restitution should be narrowed.

III.  Applications: Compensate or Disgorge?

In this Part we analyze the main types of cases that pose two questions: (1) Should the law compensate or disgorge? And (2) should liability depend on reasonableness? The first type of cases involves accidental harms, and the second type involves benefits, either accidental or intentional. For all cases, we assume that transaction costs preclude contracts.

A.  Accidental Harms

The most common harm cases that tort law deals with are accidents. Under current law, liability for accidental harms is either strict or conditioned on the injurer’s negligence. If liable, the injurer must compensate the victim for the resulting harm, which implies the internalization of harms (either Rule H1 or H3). The choice between strict liability and negligence rules has been thoroughly discussed in law and economics (and other) literature.[32] In contrast, the choice between compensatory and disgorgement damages for accidents went unanalyzed until a few years ago. Is disgorgement of the injurer’s gains from omitting precaution an adequate remedy? The following example, discussed in the Introduction of this Article (with a small adjustment relating to the probability of infliction of harm) and borrowed from a previous article,[33] illustrates the dilemma whether to allow disgorgement damages for accidents.

Example 1A. Omitting a Test. Doctor in a public hospital performs a beneficial procedure for a patient. In addition to the benefit, the procedure risks harmful side effects. A test that costs Doctor 20 can prevent the harmful side effects. Omitting the test causes harm of 1,000 to the patient in 10 percent of cases. Doctor omits the test and the harm materializes.

In this example, courts apply Rule H3 (negligent liability for harm with compensatory damages) and award damages of 1,000. With this rule doctors have efficient incentives to take care, so the doctor in Example 1A will administer the test as efficiency requires. Theoretically, the law could adopt instead Rule H1: strict liability for harms. With this rule, the doctor in Example 1A will also administer the test.

Consider now the possibility of applying the rules of disgorgement damages for accidents (DDA) to Example 1A: either Rule H4 (a negligence rule) or Rule H2 (a strict liability rule). Under Rule H4 Doctor’s liability is 200, rather than 1,000.[34] With DDA (plus epsilon), the doctor will administer the test as efficiency requires. Liability for 200 instead of 1,000 might provide doctors with incentives to increase their activity level. On many occasions this is a shortcoming of Rule H4, but with doctors’ liability it might be a virtue, since doctoring produces positive externalities.[35] Also, if doctors are subject to chilling effects and as a result are overdeterred or practice defensive medicine, liability of 200 rather than 1,000 would ameliorate the problem.[36]

Rule H4 would also improve victims’ incentives to take precautions and reduce their activity levels. In Example 1A, liability of 200 (undercompensation) would provide patients with stronger incentives than liability of 1,000 to take precautions and reduce their risks.[37]

In order to apply Rule H4, courts need information about the costs of untaken precautions and the probability of harm if precautions are not taken.[38] In Example 1A this information might be available to courts. In other cases, it is not available and the compensatory negligence rule (H3) might be easier to implement.

Returning to accidental harm, suppose now that liability for disgorgement damages is strict (Rule H2) rather than conditioned upon the doctor’s negligence (Rule H4). In accident cases, would strict liability with disgorgement damages (Rule H2) have advantages over strict liability with compensatory damages (Rule H1)? Under Rule H2, the injurer’s liability is the cost of untaken precautions divided by the probability of harm. Thus, assume that the doctor could have reduced the risk to the patient to zero by taking tests that cost 200 rather than 20. Under Rule H2, if Doctor omits the tests and harm materializes, Doctor’s liability would be 2,000 (which is twice the harm caused to the patient). As precautions are taken, Doctor’s liability continues to fall even when precaution exceeds the efficient level. Consequently, there are excessive incentives to take care. Indeed, Doctor has an incentive to take care up to the accident-eliminating level of care, which is 200 and reduces the patient’s risk by only 100. Rule H2 is therefore inefficient: it provides excessive precautions for injurers to take care and reduce their activity level. It also encourages victims not to take care, since  injurers will eliminate any risk they create (assuming no contributory or comparative negligence defense is available).

B.  Rescue Cases

1.  Reasonable Restitution for Benefits

The rule that benefactors who conferred unrequested benefits on beneficiaries are not entitled to any compensation from them has a few exceptions. One is rescue cases, including cases in which the benefactor protected the recipient’s life, health, property, or other economic interest when the latter’s timely consent could not be obtained. Timely consent is impossible in emergencies. Under certain conditions, the law allows the benefactor to recover a reasonable charge for beneficial actions.[39]

Consider the following case:

Example 3. Rescuing a Car. During a storm Rescuer, a bystander, observes Recuee’s car being swept into the river. Getting Rescuee’s consent is impractical, so Rescuer takes reasonable steps and saves the car. Rescuer’s efforts cost 20, while the value of the car which was saved is 100. The probability of the rescue’s success at the time it took place was 100 percent.

Under current law Rescuer is entitled to compensation of 20, which equals the reasonable costs he spent for saving the car (Rule B4).[40] Under an alternative rule, Rescuer would be entitled to disgorgement of 100 (the value of the car), given his reasonable efforts in rescuing the car (Rule B3).

Under Rule B4 Rescuer has efficient incentives to save the car because he would be able to recover his cost of 20. Alternatively, if precautions had cost, say, 200, so that the rescue had been inefficient, Rescuer would not have saved the car because he could not have recovered more than reasonable costs.

Note that in Example 3 the probability of the success of the rescue is 100 percent. If instead it were less than 100 percent, Rule B4 would allow Rescuer to recover more than his costs. Specifically, he would recover his costs divided by the probability of success. Rule B4 deviates from prevailing law under which the magnitude of Rescuer’s damages does not depend on the probability of success.[41] (We do not consider another possibility with equivalent incentives: the rescuer recovers his costs whenever he attempts a rescue, regardless of whether the attempt succeeds or fails; the parallel alternative in harm cases is to impose liability for expected rather than materialized harm.)[42]

Rescuer, however, under Rule B4, does not have efficient incentives for his ancillary activity of rescue since he gains nothing from saving the car. Thus, if Rescuer is a professional rescuer, who could invest in equipment for rescue before any specific rescue becomes concrete or increase his rescuing activity by, say, making intensive searches to find people in need of a rescue, with only compensation for his reasonable efforts, he would not do any of those activities.

What about Rescuee’s incentives? When Rescuer makes efficient efforts to rescue, Rescuee internalizes the increases in the rescue’s worth due to his own actions, so Rescuee has efficient incentives for precautions. Thus, if reasonable efforts by Rescuer will leave the saved car with some harm, and Rescuee could take steps and prevent that harm, Rescuer would take those precautions if they cost less than the expected harm to be saved by them.

Rescuee would also have an efficient activity level. In conducting his activity, Rescuee will take into account that he might need a rescue, and that he would bear the costs of such a rescue (by compensating Rescuer). Internalizing the costs of rescue thus provides him with incentives for an efficient activity level.

Applying Rule B4 requires the court to observe the burden of the rescue, the probability that the benefit materializes, and whether the rescuer’s efforts do not exceed the efficient level. This information is often available to courts.

Imagine now that instead of Rule B4 (compensation), courts apply Rule B3 (disgorgement). According to this rule, as long as Rescuer invests efficiently in rescuing, he is entitled to disgorgement damages at the amount of 100 (the car’s value). Under this rule, Rescuer’s incentives are efficient: he invests in the rescue at the efficient level, which in Example 3 is 20, but would not invest 200. Furthermore, Rescuer’s ancillary activity (investing in equipment and conducting searches for people in need of rescue) is also efficient since under Rule B3 Rescuer fully internalizes the benefits of his rescuing activity.

So far it seems that Rule B3 is more efficient than Rule B4. This impression changes once Rescuee’s incentives are considered. With Rule B3 (disgorgement), Rescuee has no incentives to take precautions to increase the rescue’s value (such as preventing some harm to the car if rescued) since that value would go to the rescuer. Furthermore, he would take excessive precautions to rescue himself to avoid being in need of rescue in the first place and might also take too low of an activity level. The reason for this is that if he is in a need of rescue, he is rescued, but still loses the value which has been rescued instead of just paying for the costs of the rescue (as under Rule B4 (compensation)).

Applying Rule B3 requires the court to observe the value saved and assess whether the rescuer’s efforts do not exceed the efficient level. This information is often available to courts.

In sum, while Rule B3 is better than Rule B4 with respect to Rescuer’s incentives for his ancillary activity, this rule is much worse with respect to Rescuee’s incentives for both his precautions and activity level. Our comparison between the two rules might explain why professional rescuers—such as doctors who provide first aid—are entitled to more than just costs of rescue.[43] By allowing damages higher than costs, professional rescuers’ activity levels are improved.

Our discussion in this Section has two policy implications:

First, when Rule B4 (compensation) is applied, Rescuer should recover more than his costs if the rescue’s probability of success was less than 100 percent (or alternatively, Rescuer would be allowed to recover his costs regardless of success).

Second, the choice between Rule B4 (compensation) and Rule B3 (disgorgement) should depend on the tradeoff between better incentives for Rescuer’s ancillary activity (Rule B3), and better incentives for Rescuee (Rule B4). An amount between compensation and disgorgement might sometimes be a good compromise, as in cases of professional rescuers.

Our recommendations for higher compensation than actual costs, either according to the first or second policy implications above, are limited to cases in which there are no prior relationships or interactions between the parties and manipulation is not plausible. If this is not the case, other considerations should count as well. If Rule B3 (disgorgement) applies, there is a risk that rescuers would put rescuees in peril and then rescue them and gain profits.[44] If Rule B4 (compensation) applies and allows recovery which is higher than actual costs (when probability of success is less than 100 percent), rescuers might also put rescuees in peril, then rescue them, and manipulate the court by underestimating the probability of success.

2.  Strict Restitution for Benefits

Suppose now that rules of strict restitution for benefits are applied. According to Rule B2 (compensation), Rescuer is entitled to recover any costs, reasonable or not, that he spent on the rescue; according to Rule B1 (disgorgement), Rescuer is entitled to recover disgorgement regardless of the costs he spent on the rescue.

Rule B2 (compensation) provides incentives for rescuers to invest too much in the rescue, since the rescuer is entitled to compensation for all his costs divided by the probability of rescue. Thus, Rescuer is indifferent to all levels of efforts, reasonable or not, and if he is paid a bit more than his costs divided by the probability of rescue, he has excessive incentives to rescue (still, his ancillary activity is deficient for the reasons elaborated on above[45]). Rescuee’s incentives are also inefficient: knowing he would pay for rescue beyond reasonable costs, Rescuee would overinvest in rescuing himself or avoiding the need of rescue and might even reduce his activity level. Thus, Rule B2 has no advantages whatsoever.

Rule B1 (disgorgement), in contrast, provides efficient incentives for rescuers with respect to both precautions and ancillary activity. The reason for this is simple: with full internalization of costs and benefits, Rescuer will behave efficiently.

Rule B1, however, is problematic for Rescuee’s incentives for the same reason that Rule B3 is problematic:[46] Rescuee knows that when he is in need of a rescue and is rescued, he still loses the value which was rescued instead of paying for the social costs of his rescue. As a result, he would not try to increase the value of the rescue; he would take excessive precautions to rescue himself or avoid the need for rescue and would reduce his activity level.

C.  Common Funds and Analogous Cases

Another category of cases in which the law allows benefactors to recover for unrequested benefits is “common funds.” Common funds are monies obtained through legal proceedings initiated by one party (or the party’s attorney) against which others can assert claims.[47] Under certain conditions, the initiator of the legal proceedings who incurred expenses to benefit a group of people can collect an equal share from each of them, even if they refused to back these efforts at the outset.[48] An illustration is the case of an heir who initiates legal proceedings resulting in an increase in the value of the estate, to the benefit of the other heirs.[49] Liability in common fund cases is aimed at overcoming the free-riding problem which might hinder the preservation or creation of a common fund; without legal intervention each beneficiary would hope to free ride on other beneficiaries’ efforts, so no one would act to preserve or create the common fund.

In previous publications[50] we argued that efficiency considerations justify expanding the duty of restitution beyond common fund cases to require compensating benefactors for unrequested benefits when the following conditions are met: (1) high transaction costs preclude reaching an agreement for payment of benefits between the benefactor and beneficiaries; (2) risk of overvaluation is low; (3) enforcement costs do not exceed the benefit of the expanded duty of restitution; (4) the benefits will not be created either by other state action or by market mechanisms; and (5) the beneficial activity does not have offsetting welfare-reducing effects.[51]

The main application for this expanded duty of restitution is the private production of public goods when, absent legal intervention, free riding and other transaction costs bar their production.

Consider the following example discussed in the Introduction:[52]

Example 2: Constructing a Garden. Builder considers constructing a garden on her land that will increase the market value of her house and five Neighbors’ houses. The garden costs Builder 15. The increase in the value of Builder’s house is 10, and the increase in the value of each Neighbor’s house is 2. The benefits are a public good: Builder cannot prevent Neighbors from enjoying the garden’s benefits once it is created. Since each Neighbor knows that her benefit from the public good does not depend on her contribution to its costs, she contributes nothing, hoping that Builder and the other Neighbors will pay for the garden. However, since all Neighbors reason in the same way, nobody pays. Nevertheless, Builder constructs the garden, conferring a total benefit to Neighbors of 10.

Legal intervention under restitution law could take several forms, including the adaptation of any of Rules B1–B4. To avoid repetition, we will consider two rules only: Rule B4 (compensating for reasonable costs) and Rule B3 (disgorging the benefits accrued due to the benefactor’s reasonable efforts).

Under Rule B4 (compensation) Builder should recover costs of 7.5 from Neighbors (1.5 from each) because they are reasonable. Consequently, she has efficient incentives to construct the garden.[53]

Things become more complicated if Builder could affect the distribution of the benefits between her and Neighbors in unverifiable ways: she is likely to construct the garden in such a way that more benefits go to her rather than to Neighbors, even if such construction is inefficient. We assume that such behavior would be verifiable and if she does so it would adversely affect her amount of recovery from Neighbors.

Also, Builder’s activity level might be inefficient. To see why, imagine that Builder is in the business of developing residential areas and creating public goods, such as gardens. She needs to make investments in locating the right places for development. Since she does not internalize the full benefits she creates, she will invest inefficiently in locating the right places. In contrast, Rule B3 (disgorgement) would provide Builder with efficient incentives for both constructing the garden efficiently and for her activity level. Therefore, if it were just for Builder’s incentives, Rule B3 would be more efficient than Rule B4.

But when it comes to Neighbors’ incentives, the efficiency effects of the two rules reverse: Rule B4 (compensation), rather than Rule B3 (disgorgement), is the one providing Neighbors with more efficient incentives.

To see why, imagine that Neighbors can take steps and enhance the benefits of the garden for them (say, by constructing the windows of their homes to face the garden). Also, new neighbors could come and build homes in the area. If Rule B3 (disgorgement) applies, Neighbors should disgorge all the benefits created by Builder, so they would not incur costs in constructing windows to face the garden, and some new neighbors that would have come to the neighborhood if they had been allowed to retain at least some of the garden’s benefits would not come.

Things would be different under Rule B4 (compensation). Under this rule, Neighbors pay just for the costs of creating the benefits for them. Given this, they will take efficient measures to enhance their benefits, since those benefits will be fully internalized by them. Also, Neighbors’ decisions whether to live in the area will be efficient.[54]

To summarize, the choice between the two rules depends on whether Builder’s activity level incentives are less or more important than Neighbors’ incentives. Thus, if Builder is a professional in the business of developing residential areas, the optimal solution would be more than just covering costs. A compromise between the two rules might be to allow Builder a recovery somewhere between compensation and disgorgement.

Note that difficulties in verifying the benefits and the probability of their creation (in cases of probabilistic benefits), and whether Builder’s efforts are lower or higher than the efficient level might change the conclusion and affect the choice between the two rules.

Conclusion

This Article developed eight liability rules for harm and benefit cases and pointed out the symmetry between the rules relating to harms and the rules relating to benefits. This Article also provided an explanation for the legal divergence between tort law and restitution law and made the claim that the gap between these two fields should be narrowed. Finally, this Article applied the eight rules to the main categories of harm and benefit cases and appraised their advantages and disadvantages. The simplest model of a liability rule, which this Article uses (most of the time), assumes two actors (injurer and victim, or benefactor and beneficiary) and two actions (precaution and activity level, or benefaction and ancillary activity level). One future extension of our model would increase the number of actors and actions. Instead of two-by-two, the extension would encompass collective choice.[55]

As noted, this Article assumes that transaction costs preclude bargaining among the parties. Consequently, this Article is framed in terms of liability rules in the law of torts and restitution. Another future extension would relax this assumption and allow bargaining among the parties. Instead of framing the eight liability rules as mandatory rules of torts or restitution, the future extension would frame them as alternative contracts. We hope to consider circumstances in which parties can contract into each of the eight liability rules.

[*] *. Herman Selvin Professor of Law, Berkeley Law School.

[†] †. Alain Poher Professor of Law, Tel Aviv University; Fischel-Neil Distinguished Visiting Professor of Law, University of Chicago. We thank Omri Ben-Shahar, Vanessa Casado-Perez, Yun-chien Chang, Daniel Hemel, Alon Klement, Omer Pelled, and the participants at the law and economics workshop at the University of Chicago Law School for very helpful comments. We are grateful to Tom Zur who provided superb research assistance.

 [1]. Later we explain that sometimes compensation for costs incurred would be enough, or even better than full internalization, in encouraging efficient creation of benefits. See infra Sections I.C, I.E.

 [2].               We do not discuss non-efficiency reasons, such as protecting autonomy. See Ariel Porat, Private Production of Public Goods: Liability for Unrequested Benefits, 108 Mich. L. Rev. 189, 215–17 (2009) (discussing the concern that restitution would infringe on recipients’ autonomy and suggesting various possible methods to mitigate it).

 [3]. We assume that the increase in the value of the houses fully capitalizes the value of the garden.

 [4].               This is so under the Hand formula, first articulated in United States v. Carroll Towing Co., 159 F.2d 169, 173–74 (2d Cir. 1947); see also Restatement (Third) of Torts: Liability for Physical and Emotional Harm § 3 cmt. e (Am. Law Inst. 2005) (suggesting that negligence can be asserted by a “risk-benefit test,” where the benefit is the advantage that the actor gains if she refrains from taking precautions, a balancing approach that is identical to the Hand formula).

 [5]. See Carroll Towing, 159 F.2d at 173–74.

 [6]. Steven Shavell, Foundations of Economic Analysis of Law 80–179 (2004) (explaining that under a strict-liability rule injurers have incentives to minimize total social costs).

 [7]. The common intuition is that, with a risk of severe bodily injury, victims will take care even if they are fully compensated. This intuition is right because with severe bodily injury compensation is in fact never perfect.

 [8]. Things might be different if it were possible to distinguish between the value produced by the benefactor and the value produced by the beneficiary.

 [9]. This assumes that it is not possible to distinguish between the values produced by each actor.

 [10]. More accurately, she is indifferent toward administering or not administering the test. If, however, injuring the patient entails some additional costs (such as costs of reputational sanctions), she will probably administer the test.

 [11].               More accurately, she is indifferent toward providing or not providing the benefit.

 [12]. In more detail: because for each dollar of more benefit for herself, Builder bears the corresponding costs of creating it, she stops creating benefits when marginal costs equal marginal benefits. See Omer Y. Pelled, The Proportional Internalization Principle in Torts, Contracts, and Unjust Enrichment 34–37 (2019) (unpublished manuscript) (on file with authors) (discussing such rule in a similar context).

 [13]. This argument is valid under the assumption that the benefactor is not also the beneficiary as in Example 2. Otherwise, things would be different. See supra note 12 and accompanying text. Deficient ancillary activities by the benefactor correspond to excessive activity levels by the injurer. In more detail: strict restitution for benefits with compensatory damages causes deficient ancillary activities by the benefactor in the restitution model, and, equivalently, strict liability for harm with disgorgement damages causes excessive activity levels by the injurer in the torts model. Note, however, that under strict restitution for compensatory damages, the benefactor continues the benefaction until its marginal value is zero. If no more benefits are possible, there may be no need for more ancillary activities by the benefactor.

 [14]. Robert Cooter & Thomas Ulen, Law and Economics 207 (6th ed. 2012) (explaining how a negligence rule provides efficient incentives for both the injurer and the victim).

 [15]. Things might be different if it were possible to distinguish between the value produced by the benefactor and the value produced by the beneficiary.

 [16]. This is because he bears less than the social harm he creates (if he is not negligent, he bears no liability).

 [17]. Once the injurer takes efficient care, the victim bears all the residual harm. For further discussion of the incentive effects of Rule H4, see generally Robert Cooter & Ariel Porat, Disgorgement Damages for Accidents, 44 J. Legal Stud. 249 (2015).

   [18].               See R.H. Coase, The Problem of Social Cost, 3 J.L. & Econ. 1, 15 (1960).

 [19]. See Dan B. Dobbs et al., The Law of Torts §§ 56, 73, 687 (2d ed. 2011).

 [20]. See Restatement (Third) of Restitution & Unjust Enrichment ch. 3, intro. (Am. Law Inst. 2011) (explaining that a person who seeks compensation for benefits intentionally conferred needs to show that the benefits were requested and that the recipient has agreed to pay for them).

 [21]. See Robert D. Cooter & Ariel Porat, Getting Incentives Right: Improving Torts, Contracts, and Restitution 151–64 (2014) (providing a full account of the categories of cases in which the prevailing law of restitution imposes liability for the conferral of unrequested benefits); Porat, supra note 2, at 195–98 (same). For the argument to the contrary, see generally Saul Levmore, Explaining Restitution, 71 Va. L. Rev. 65 (1985) (justifying the law’s different approaches to harm and benefit cases).

 [22]. See supra text accompanying note 2.

 [23]. See Richard A. Epstein, Positive and Negative Externalities in Real Estate Development, 102 Minn. L. Rev. 1493, 1512–13 (2018) (arguing that the differences in people’s location, view, and preferences make it hard to treat all individuals as though they were the same).

 [24]. See               Porat, supra note 2, at 210–13 (suggesting the various possible methods of mitigating the risk of overvaluation).

 [25]. See infra text accompanying note 28.

 [26]. See generally Giuseppe Dari-Mattiacci, Negative Liability, 38 J. Legal Stud. 21 (2009) (arguing that, under a rule of negligence, it is sufficient for the law to have one sanction at its disposal since in equilibrium, there is no negligence and the sanction is never implemented; in contrast, arguing that, in benefit cases, the subsidy should be implemented again and again whenever a benefit is created by one person for another person).

 [27]. See Cooter & Porat, supra note 21, at 161 (“[W]hen the group of recipients is tightly defined and the benefits uniformly high . . . enforcement costs should not preclude restitution.”).

[28]. See William M. Landes & Richard A. Posner, The Economic Structure of Tort Law 65 (1987).

 [29]. Porat, supra note 2, at 201 (“[A]llowing injurers to force transactions on victims by unilaterally creating risks for them and then bearing all or a substantial proportion of the costs associated with those risks is essential for the occurrence of many important activities in modern society.” (emphasis omitted)).

 [30]. But see Epstein, supra note 23, at 1512–13. Professor Richard Epstein argues that occasionally injurers are constrained by the risks their injurious activities impose on themselves, while such a constraint is absent when benefactors create benefits for which they are compensated by the beneficiaries. Id. We disagree: first, very often injurers do not impose risk on themselves, and even if they do, just bearing their self-risk is not deterring enough; second, there is no reason for benefactors to create excessive benefits as long as they are compensated for the costs they incurred rather than the benefits they conferred.

 [31]. Porat, supra note 2, at 201–02.

 [32]. See, e.g., Steven Shavell, Strict Liability Versus Negligence, 9 J. Legal Stud. 1, 1 (1980) (comparing the incentive effects of strict liability and negligence rules); see also Landes & Posner, supra note 28, at 54–84.

 [33]. Cooter & Porat, supra note 17, at 250–51.

 [34]. Such a liability rule would be economically equivalent to disgorging the gains to the doctor from omitting the test regardless of whether harm materializes or not.

 [35]. See Robert D. Cooter & Ariel Porat, Liability Externalities and Mandatory Choices: Should Doctors Pay Less?, 1 J. Tort L. 1, 1 (2006) (arguing for reducing liability of doctors because of the positive externalities they create).

 [36]. See id. at 6 (“For activities with positive externalities like some medical specialties, incentives are optimal when damages are less than 100% of the victim’s actual harm.”).

 [37]. See Cooter & Porat, supra note 17, at 261–62 (arguing that under DDA, victims internalize more of the costs of their activities so they engage in less activity, and their activity levels are more efficient).

 [38]. To apply this rule, courts must know the probability that harm will occur, but it is not necessary to establish causation between omitting the test and the harm suffered by the patient. See id. at 267.

 [39]. Restatement (Third) of Restitution & Unjust Enrichment §§ 20–21 (Am. Law Inst. 2011) (discussing situations of protection of another’s life or health and protection of another’s property, in which the law allows the benefactor to recover a reasonable charge for his beneficial actions); 2 George E. Palmer, The Law of Restitution 374–83 (1st ed. 1978). See generally Hanoch Dagan, In Defense of the Good Samaritan, 97 Mich. L. Rev. 1152 (1999) (analyzing rescue cases and supporting a broad duty of restitution).

 [40]. Restatement (Third) of Restitution & Unjust Enrichment § 21(2) (Am. Law Inst. 2011) (“Unjust enrichment under this section is measured by the loss avoided or by a reasonable charge for the services provided, whichever is less.”).

 [41]. See id.

 [42]. See Ariel Porat & Alex Stein, Tort Liability Under Uncertainty 103–10 (2001) (discussing the possibility of imposing liability for creating risk and arguing that this substitution of the traditional damage-based liability might provide the solution for a number of problems that remain unsolved under the prevalent tort law doctrine).

 [43]. Restatement (Third) of Restitution & Unjust Enrichment §§ 20(1) (Am. Law Inst. 2011) (“A person who performs, supplies, or obtains professional services required for the protection of another’s life or health is entitled to restitution from the other as necessary to prevent unjust enrichment, if the circumstances justify the decision to intervene without request.”).

 [44]. See Saul Levmore, Waiting for Rescue: An Essay on the Evolution and Incentive Structure of the Law of Affirmative Obligations, 72 Va. L. Rev. 879, 886–87 (1986) (arguing that one of the reasons for the prevailing law not providing large rewards to rescuers is the moral hazard that potential rescuers will create the demand for their own services).

 [45].               See supra Section III.A.

 [46]. See supra Section III.B.1.

 [47].               John P. Dawson, Lawyers and Involuntary Clients: Attorney Fees from Funds, 87 Harv. L. Rev. 1597, 1603–12 (1974) (presenting the development of the “common fund” mechanism); Levmore, supra note 21, at 95–99 (presenting attorney-creators of common funds under prevailing law).

 [48]. Restatement (Third) of Restitution & Unjust Enrichment § 30(2)(b) (Am Law Inst. 2011) (allowing recovery in cases where “the recipient obtains a benefit in money,” thereby substantially broadening the common-funds category of cases); id. § 29 (setting out specific conditions under which a person who has incurred expenses or rendered services to preserve or create a “fund” in which others are interested may require the others, in the absence of contract, “to contribute to the reasonable and necessary expense of securing the common fund for their benefit, in proportion to their respective interests therein, as necessary to prevent unjust enrichment”).

 [49]. For examples of suits brought by an heir against his or her co-heirs, see id. § 29 illus. 23–25; Palmer, supra note 39, at 428–30.

 [50].               Porat, supra note 2, at 194.

 [51]. Another condition requires the finding that the beneficiary’s autonomy interest is not unduly compromised, a criterion not strictly relevant to the efficiency analysis we pursue here. For discussion on the beneficiary’s autonomy interest, see Porat, supra note 2, at 215–17.

 [52]. For discussion of a similar example, see Porat, supra note 2, at 191.

 [53]. Since Builder creates at the same time benefits for herself and for others, also under Rule B2 (strict restitution for benefits with compensatory damages), Builder has efficient incentives to construct the garden as long as she is compensated for a relative share of her costs. See supra note 12 and accompanying text.

 [54]. Note that Neighbors would have efficient incentives to enhance the value of living near the garden if they paid Builder a fixed amount, unrelated to their actual benefits from the garden. If this fixed amount were set at the level of Neighbors’ expected benefits from the garden given an efficient level of efforts to enhance their benefits from the garden, both Builder and Neighbors would have efficient incentives to increase social welfare. Still, Neighbors’ activity levels (their incentive to move to the area) would be too low.

 [55]. See, e.g., Ariel Porat & Robert E. Scott, Can Restitution Save Fragile Spiderless Networks?, 8 Harv. Bus. L. Rev. 1, 5 (2018) (developing an informal model that specifies rights of restitution for network members).

 

Convergence and then Downstream Divergence in Torts and other Law

Saul Levmore[*]

Introduction

All legal systems discourage theft, negligence, and other destructive behaviors, but they do so in disparate ways. They converge as far as many of their aims and starting points are concerned, but eventually they diverge in their details. My claim in this Article is that, at least in the case of tort law, there is a pattern to this descent. The divergence has a recognizable cause and is therefore fairly predictable. Specifically, I argue that convergence is associated with laws that are both efficient and attractive—a term that conveys a shared ethical intuition in the society governed by these laws. Divergence, on the other hand, arises around rules or standards that are unnecessary on efficiency grounds—because alternatives seem equally efficient—and that do not reflect some commonly held ethical sensibility.[1] Inasmuch as these terms, as well as this ambitious claim, are open to debate, it is useful to consider a number of legal problems and treatments, both legislative and judicial, in order to clarify and appreciate the claim. The argument draws on elements of comparative law, the reality of shared ethical sentiments within a society, the economic analysis of tort theory, and the limits of empirical work. In this Article, the claim is limited to torts but, as suggestive examples will show, it can be turned into a conjecture that includes other areas of law,[2] and that pertains to both rules and standards.[3] It might also say something about areas in which law outsources decisionmaking to markets, but that subject is left for another day.

I.  Binary Constructions: Contributory and Comparative Negligence

In many jurisdictions, tort law long ago settled on an axiom that is binary in form: liability is assigned to a negligent party who caused harm; causation is also an all-or-nothing game. Law, more generally, vacillates between binary rules and smoother, multifactor ones. A either murdered B or did not; there is no punishment when there is a 30 percent chance that A did it. Similarly, in tort law’s treatment of negligently caused injuries, the long-standing tradition was, first, if C was 70 percent likely to have negligently caused D’s injury, C paid 100 percent, and second, that liability was completely forgiven when the injured party, D, was also negligent.[4] To be sure, there was, and remains, divergence at the first step because some activities were subject to strict liability; still, when this regimen was in force, liability was withdrawn in certain cases if the injured party’s negligence contributed to the injury.[5] Tort liability was thus regularly all–or–nothing, or what I am calling binary, even when law might instead have shared liability between the injurer and injured parties. Several features of this characterization require examination. A newcomer to the legal system might ask where these categories came from and why they are necessary. A more difficult but somewhat tangential question is why and when laws come in binary form. This is especially relevant here, because the binary character is an important starting point for the claim that convergence is located where efficiency and shared ethical sentiments find common ground.

It is apparent that categories as well as binary rules facilitate simplified instructions to those who must make everyday decisions with legal threats hovering nearby, and this is itself a form of efficiency. Categories also smooth the work of government officials asked to judge or enforce laws. The more complicated an organization, and the lower the cost of false positives, the more attractive are binary rules. For example, a law requiring drivers to be at least sixteen years old might be sensible, even though age is an extremely rough proxy for what the law really wants of drivers, including skill, informed judgment, and an appreciation of risks. This is because the cost of barring skilled but underage drivers is low, especially when they are on notice not to invest in early training or in jobs that require them to drive, or where there is public transportation. It might be more efficient to count on insurance markets, concerned parents, or direct and cleverly designed fees to encourage safety training, or even to determine the age at which driving is permitted for particular individuals. However, generalization seems low cost and politically acceptable (note the hint of shared ethical intuitions here); it also makes enforcement easier as very young (illegal) drivers can be identified and removed. In fact, once automobiles came into wide use, virtually every jurisdiction established a minimum age requirement for drivers, as opposed to a standard or to no intervention by the state at all.

However attractive legal systems find binary categorization,[6] it comes at a cost. Categories can be foolish. Thus, people are unlikely to be entirely introverted or extroverted, or cruel or kind, however natural it may be to imagine these binary forms.[7] In some cases, binary legal judgments are attractive because more refined, multifactor decisionmaking is not only costlier to process but also likely to bring on the risk of corruption, at least where the new variables call for judgment rather than straightforward measurement. A standard gives a regulator more discretion, and thus invites common sense, but also abuse.[8] Binary rules make it easy to treat like cases alike, and thus lower a source of discontent by disappointed parties. Much of this is familiar from the rules-versus-standards literature, but some caution is required. An apparent rule might require a great deal of discretionary decisionmaking; thus, negligence and contributory negligence (discussed below), like “net income” in tax law and so many other legal “rules,” are better thought of as standards than as rules. This is in part why it is misleading to associate either binary or multifactor guidelines with what are conventionally described as rules.

The popularity of a negligence or strict liability approach, accompanied in the academic literature by a binary contributory negligence defense, is from this perspective unsurprising. Its efficiency is well known.[9] In the case of automobiles, for example, a driver has reason to be careful because he has no reason to expect that another driver will also be negligent in a way that causes the two to crash. The second driver also has reason to take care because she will know that recovery is unavailable if she does something like speeding out of a driveway without looking and is then hit (even) by another speeding vehicle unable to be stopped in time. Again, describing the law as binary, refers to the fact that liability is all–or–nothing when it might easily have been shared between the two parties.

A more global explanation for the prevalence, or convergence, of the binary character of many laws, is that it suppresses evidence of voting paradoxes.[10] If a decision is to be made by multiple voters or other decisionmakers and there are more than two variables, it is easy for the decisionmakers to be unable to reach a stable result. They might cycle among the available options or be disgruntled when they can see, after the smoke clears, that a majority opposes the decision reached by a legislature or other body of voters that claimed to be governed by majority rule. A majority may prefer outcome X over Y, and then Y over Z, but Z might be preferred over X. Motion-and-amendment voting, found in legislatures around the world and popularized by Robert’s Rules of Order in the case of sizeable private organizations in the United States, finds a Condorcet winner—which is to say an option that defeats all other options in head-to-head competition—if one exists.[11] Motion-and-amendment voting allows X to win if it is preferred over both Y and Z, and all other proposals, but it hides the fact that there is no real, consistent majority winner where X beats Y, Y defeats Z, and Z is preferred over X. This voting method does this by always asking for binary decisions and then making it difficult to revisit an option once the option has lost in a head-to-head competition. With its binary decisions, law thus hides evidence of cycling preferences but does an excellent job of finding desirable, Condorcet winners where they exist. This might explain why legislatures are normally asked to vote a proposal, or any amendment or substitution to it, up or down, and why panels of judges on appellate courts, in binary style, affirm or reject rulings that they hear on appeal.[12] Indeed, this is a remarkable example of convergence across legal systems, though I am unsure whether to call it efficient (as it avoids repetitive cycling) or simply politically attractive (as it prevents the outrage expected of people when they see that a majority opposes the result found by another alleged majority). Though this is not unique to tort law, it is useful to see that where there is little risk of cycling, as when preferences are “single peaked,”[13] law is more hospitable to putting multiple variables or ranges on the table.

A good example of the emergence in tort law of a non-binary approach where there is little risk of cycling, and where there is no loss of efficiency and even a gain in terms of law’s ability to conform to political and ethical expectations, is the emergence of comparative negligence. Its predecessor, contributory negligence, is binary in form; a wrongdoer is absolved if the injured party was also negligent. In contrast, comparative negligence, under which the fact-finder spreads liability according to the relative wrongdoing of multiple parties, is more continuous as well as increasingly popular.[14] There are two useful ways to think about the emergence of comparative negligence. First, citizens find comparative negligence attractive because they seem to dislike the idea that mere negligence can reduce an injured party’s recovery all the way down to zero. The shared ethical sentiment is to favor comparative over contributory negligence. This sentiment may be motivated by a fear of mistaken fact-finding, though I hesitate to put too much weight on this conjecture because it introduces a kind of efficiency argument to what is essentially one about ethical sentiments. It seems unlikely that many citizens or legislators think about enforcement costs when they opine about fairness in tort law. A better description might therefore draw on a theory of justice or an evolved taste for retribution. An obvious question is why older law did not reflect these ethical intuitions. One answer is that perhaps we cannot know what ancient shared ethical intuitions looked like. Another, and one with some support in the historical record, is that some lawmakers inserted a version of comparative negligence by quietly reducing damages when the injured party was also negligent.[15]

The second characteristic of the emergence of comparative negligence in tort law returns us to cycling preferences. Imagine decisionmakers deciding whether to award full damages, partial damages, or zero damages to someone who was injured by a speeding driver, but who was arguably contributorily negligent, perhaps by suddenly emerging from a hidden driveway. One fact-finder might rank the desirability of results as Full-Partial-None—where Full means that all of the liability is assigned to the speeding driver on the roadway, and is the fact-finder or decisionmaker’s first choice, Partial means that the first driver pays a fraction of the loss suffered by the negligent victim, so that the two divide the loss, and so forth. Another voter might have the opposite inclination, reasoning that law should strongly discourage drivers from darting into a public road, so that recovery by the negligent injured party should be completely denied. But it is hard to see why anyone would rank Partial last. A voter, or jury member, who thinks the plaintiff should recover full damages will surely be happier with a partial recovery by this plaintiff than with no recovery at all. Similarly, one who thinks that contributory negligence should bar recovery, would certainly prefer partial recovery over full recovery if she cannot have her first choice of None. If so, there is no danger of cycling; Full will beat None, or None will defeat Full, or there could be a tie between these two, but there is no chance that the winner of the Full-None competition will then lose in competition with the Partial option. Partial liability can certainly be a voter’s first choice, and it is almost surely the second choice of those whose first choice is either Full or None, but it is hard to imagine Partial (liability) as anyone’s third choice, and for this reason there will be no cycling. Similarly, the common rule barring anyone under the age of sixteen from operating a motor vehicle is a binary rule where there is no danger of cycling.[16] It is telling, and certainly interesting, that law has moved away from the binary approach of contributory negligence just where there is no apparent risk of cycling preferences.

It is noteworthy that the non-binary form of modern comparative negligence was first introduced in European admiralty law, where judgment was rendered by a single lawmaker who was, therefore, in no danger of cycling.[17] Indeed, it is tempting to say that legal systems that rely on a single judge rather than a jury will be quicker to adopt comparative negligence, though this hardly explains Hammurabi’s Code and other long-standing uses of contributory negligence. But the argument here suggests that juries are unlikely to cycle within a comparative negligence framework, so it is unsurprising that comparative negligence emerged in a wide variety of jurisdictions.[18] Similarly, it is not surprising that comparative negligence comes in many forms; none of these forms would come in last place, and any could emerge in a divided group of voters.

This first example illustrates the idea that there is convergence up high where ethical sentiments and efficiency considerations are in sync. Virtually all legal systems find a means of discouraging negligent behavior toward strangers. This example also supports the claim that divergence arises downstream, when it comes to detail, where ethical intuitions and efficiency considerations are at odds, or where efficiency can be promoted with a variety of legal directives.[19] To be sure, the argument would be better if there were no excluded class; once there is convergence upstream, we do not get to observe whether downstream divergence proves much. My claim might seem obvious or even circular. A better example might be one with upstream divergence and then downstream convergence. It is thus convenient to point to the fact that virtually all systems converge on awarding single damages in tort law, presumably to avoid moral hazard. At first, this example of upstream divergence and downstream convergence will seem contrary to the theory advanced here, and certainly to the title of this Article, but it shows that the theory is hardly obvious or tautological. Where different rules are all efficient, legal systems can afford to be divergent, though they might eventually evolve to a single rule if there develops a shared ethical intuition in its favor. But where efficiency favors a single rule—as it does for single indemnity to combat moral hazard—and there is no shared ethical intuition that contradicts this rule, we find convergence. Here we have rare cases where this convergence-divergence pattern is of the downstream-upstream form, respectively, though usually it is the reverse.[20]

II.  Other Examples in Tort Law

A.  Negligence: Strict Liability and Rescue

The choice between negligence and strict liability is perhaps the most obvious and far-reaching example of the theory developed here. Another, yet narrower, example concerns the familiar question of whether there ought to be a duty to rescue.[21] But inasmuch as both of these examples are now obvious and inadvertently addressed elsewhere, they merit just a few words. Again, legal systems must discourage avoidable and intentionally caused injuries. They can do so with a variety of approaches, and of course we find divergence among legal systems.[22] The convergence is with respect to a law that requires one actor—including negligent and wrongful ones—to pay for the loss inflicted on an innocent party. The divergence is in the choice of negligence or strict liability, and then in the treatment of exceptional cases, where a negligence–based system opts for strict liability, or where a system or subsystem that chooses strict liability as its default switches to a negligence formulation.[23] Both approaches are consistent with the idea that tort law promotes efficiency, although reasonable people can disagree as to which is superior once activity levels and enforcement costs are taken into account. This uncertainty might be said to “explain” the divergence between the two approaches. The same is true once ethical sentiments come into play, as the approaches diverge just as these sentiments do.

In the case of a failure to rescue a person in danger, or even to save another person’s property that is at risk, there is variety among legal systems[24] and also disagreement about the efficiency of the various approaches.[25] Where human life is at stake, the shared ethical sensibility is quite clear; it is widely thought that one ought (or is even bound) to rescue another where there is little danger to the rescuer.[26] Indeed, this is an excellent example of the proposition that shared ethical sentiments alone do not predict law, and certainly not convergence of law. There is less agreement about rescuing another’s property when the rescue might be unsuccessful, where rescue requires trespass, and where destruction is unlikely to be immediate. But as an efficiency matter, there is the problem, perhaps just theoretical, that a duty to rescue persons might encourage people to avoid “rescue spots,” and also the problem that so many potential rescues involve multiple parties who might truly believe that someone else has called for help; over-rescue can be inefficient or even dangerous.[27] It might also be difficult to judge when the risk is immediate; a rescuer might claim there was imminent harm when in fact professional help could have been summoned, or there was no threat of harm in the first place. Again, we see variety among laws where there is not agreement between ethical intuitions and efficiency considerations.

B.  Incapacity Exceptions

It is tempting to deflect criticism that this Article is engaging in a form of ex post data fitting by claiming that the ideas offered here fit every nook and cranny of tort law.[28] It is more useful, I think, to limit our inspection to one additional, small application in the law of torts, and then to postpone for future work an expansion to other areas of law. There is great divergence among jurisdictions when negligent behavior by children, insane persons, and other incapacitated defendants have caused injury.[29] Again, there is no shared ethical intuition, as we sometimes excuse the incapacitated person and at other times empathize with the injured victim. On the other hand, there is some de facto convergence, as when an insanity defense tends to be followed by a period of confinement about the same as the length of incarceration for more typical, convicted criminals. Note that ethical intuitions support this similarity in detention.[30] There is also no clear category or principle to separate cases where it is clear that efficiency calls for liability or an exception to the default category of negligence (or strict liability). In the case of young children, for example, liability might lead to optimal supervision by their guardians, but it might also detract from desirable learning, something courts have noted.[31]

III.  Expanding the Theory Outside of Tort Law: From Trust Games to Voting

The ideas offered here are interesting but in some areas they are hard to pin down. It becomes apparent that both efficiency and convergence are imprecise terms, and yet the theory is enticing even outside of conventional legal topics. Consider the first-year curriculum of most law schools. The schools teach torts, civil procedure, and contracts, and thus converge. They then diverge, as predicted, one or two steps downstream when it comes to the length of these courses, the cases that are assigned, the mix of theory and doctrine, and the time spent on particular subjects.[32] The argument would be that it is sensible or “efficient” to begin with these subjects because they prepare students for more advanced courses, though these courses might themselves reflect arbitrary but useful categorization; the schools could just as easily have converged on a course titled unjust enrichment or free-riding. It would be difficult to insist on shared ethical intuitions and, as for efficiency, we do not really know that the convergence in curricula, if it is that, is efficient. There is certainly no controlled experiment in which the emergence of good lawyers or even of impressive bar-passage rates is compared with that of comparable students who experience a different first-year curriculum. To the contrary, no law school appears to discriminate among applications to be admitted as transfer students based on the details of the first-year courses these applicants experienced in other schools. Here, as in so many other institutional practices, there is initial convergence because of intuitions or imitation and, more interestingly, subsequent divergence where there is no way to assess or theorize about the most efficient or ethically attractive details.

Returning to legal systems, rather than the way they are taught, it is noteworthy that they have also converged over time in the way they punish or disable convicted criminals. Nevertheless, they diverge as to the length of imprisonment. It is easy to regard this as another example of basic convergence and subsequent, downstream divergence, but much harder to associate that which converges to a combination of efficiency and shared ethical sentiments. The best we can say is that there is less agreement about these things in questions of length, rather than manner, of punishment. In some cases, efficiency is a matter of theory rather than empirical evidence, as it is for negligence and strict liability, as well as contributory and comparative negligence. The pairs are interchangeable as a theoretical matter, and that is enough for the theory advanced here. If so, we can say that, in theory, imprisonment should deter crime, but when it comes to the length of sentences there are decent arguments for shorter and longer sentences, not to mention more or less substantial gaps as one moves from less serious to more serious crimes.[33] No doubt, divergence also comes from disparate circumstances. A society with little water will probably impose greater criminal penalties for the destruction of a well; cattle rustling (or “duffing”) was treated with severe penalties in the Old West as it was in many countries, and not because the thieves were harder to apprehend. These examples of downstream divergence are best described as responding to different shared ethical sentiments or political pressures, although strained efficiency arguments can be made. Either way, law and politicians obviously respond to outcries, though we might think of these as examples of local ethical sentiments that are fairly predictable.

This optimism suggests that we ought to find divergence even on basic principles where there is neither a common ethical intuition nor empirical evidence or theoretical support for one legal tactic.[34] Many examples will come to mind, but two should suffice. Consider the choice of voting systems. There might be theoretical and even ethical reasons to expect democracy, but divergence begins almost immediately when it comes to its form. We cannot identify the best voting system and of course we find great diversity in this area.[35] The example suffers from the fact that there is a great deal of copying among jurisdictions, but even if we subscribe to the idea of looking for convergence through spontaneous ordering,[36] the divergence is impressive. Convergence is thus limited to questions that are essential for democratic systems, and this fits nicely with the idea that we find convergence where efficiency considerations (broadly defined in this case) and shared ethical sentiments converge.

The same might be said for how democracies function. Consider the decision of a city’s mayor to divert some funds from the anticipated purchase of police cars to the idea of putting some officers on bicycles. The intuition is that these officers could then better patrol a recreational area or interact with citizens. Bicycles might also help keep some officers physically fit, and citizens might simply like them or be inspired to be more fit themselves. The decision is almost impossible to evaluate. Crime or fitness may have increased or decreased after the introduction of bicycles, but so many other factors could cause these changes, and it would be absurd to attribute a dramatic change in crime rates to a small change in the mixture of police vehicles in a large city. It may be ethically and politically irresponsible to run an experiment in which the number of bicycles is randomly altered, and in any event even a sophisticated use of artificial intelligence will find it difficult to overcome the problem of omitted variables.[37] In practice, there is divergence among jurisdictions where efficiency is difficult to determine, and where there is unlikely to be a shared ethical intuition. I suspect that when a serious crime occurs in a location accessible by bike but not by car, there is the intuition that some officers on bicycles would be a good idea. For this or other reasons, there may be convergence by imitation so that we expect at least a few bicycles in every large police force.

Finally, there are subjects where other forces are likely to overwhelm the boundaries suggested here between convergence and divergence. Convergence may, for example, come about because it is of lower cost than innovation and divergence. One can hire officials or draft laws at lower cost if they have been trained or written elsewhere in a particular mode. On the other hand, divergence may be attractive because there is a market for it. Following Professor Charles Tiebout’s well-known hypothesis,[38] a jurisdiction may opt for more or less spending on a good, or on a different legal approach, in order to attract businesses or citizens that prefer that law in the mix they will encounter in the adopting jurisdiction. This form of strategic, market-like diversification might be more apparent the less fundamental the laws, but in some cases it is seen upstream with respect to basic principles, as in the promise by some jurisdictions not to have an income tax. This source of divergence seems unlikely for tort law. A business might choose not to sell a product in an area known to award very high damages in cases of products liability, but it is unlikely that a jurisdiction will gain much by choosing to apply the negligence principle, or an exemption from any liability claim at all, to products, if only because mobile firms normally expect that many of their products will be used in other jurisdictions. One jurisdiction might care more about income redistribution than another, but I prefer to think of this as a subset of what this Article has called ethical intuitions—and thus expect divergence. Though, I note that while academics associate strict liability in tort law with redistribution to poorer consumers, strict liability in fact is often capped at absurdly low amounts that promise to leave wealth in the hands of the owners of many corporations. In any event, Tieboutian logic in favor of diversity is probably better associated with a divergence in jurisdictions’ spending decisions than with threats of liability.[39]

Conclusion

Complete convergence among legal systems is implausible for several reasons. Decisionmakers have reason to copy the laws and practices of other jurisdictions—if only to avoid criticism when things go wrong—but also to distinguish themselves, and then hope for the best. Somewhat similarly, judges have good reasons to follow precedent, but also to diverge on occasion, whether openly or by asserting that a case is one of first impression. This Article has suggested a different, but coexisting, reason for convergence and divergence in tort law, as well as in other far-flung areas of the law. Convergence is associated with efficiency alongside shared ethical sentiments. Where a variety of legal techniques seem equally likely to be efficient, or where ethical intuitions do not match identifiable efficient laws, divergence is expected. A second part of the theory advanced here is that the details of laws are less likely to be uniquely efficient and also less likely to match shared ethical sensibilities. As such, there is almost always divergence as legal systems take fundamental principles and then experiment with, or simply use their experiences or political and social characteristics to fashion, details on the ground. An empirically minded optimist might look at the examples provided here and suggest that divergence offers lawmakers natural experiments, and that these will soon enough lead to more convergence further downstream. I have suggested, and will extend the argument in future work, that this intuition about the impact of empirical work is too optimistic, because as we move downstream it becomes harder to assemble useful empirical evidence. Rules may come to dominate the terrain,[40] but we should continue to expect divergence in the details—or more technically, in areas where we cannot identify the most efficient legal rule and where there is no widely shared ethical sentiment. These claims about convergence and divergence were demonstrated in this Article with cases drawn from tort law, and in future work I hope to show not only that these claims hold true for many other areas of law, but also that they are necessarily true for the reasons hinted at here.

 

[*] *. William B. Graham Distinguished Service Professor, University of Chicago Law School. I am grateful for comments received at a University of Chicago Law School workshop, from participants in the conference memorialized in this issue of the Southern California Law Review, and over the years from Richard Epstein and Ariel Porat. Better colleagues would be impossible to find.

 [1]. Note that these intuitions can come from very different reasoning processes. Twenty citizens are likely to agree that murderers should be disabled, but they might have twenty different reasons for this view or even for the question of what incarceration will accomplish.

 [2]. As the claim is expanded beyond tort law, it is easier to find exceptions to the idea advanced here. Exceptions may well prove the rule, but it is useful or simply safer to think of the thesis developed here as limited to torts, and to expand the argument to other areas of law in the future.

 [3]. It is worth insisting at the outset that characterizing laws as binary, convergent, divergent, or multifactor is not, as we will see, the same as marking them as rules or standards. There is of course the danger that the upstream-downstream distinction is too malleable. But in many cases that support the theory offered here, the distinction seems unassailable. A country is upstream from a city; deterring theft and murder is upstream from the number of years of imprisonment a thief or murderer is ordered to serve.

 [4]. See William M. Landes & Richard A. Posner, The Economic Structure of Tort Law 3, 88 (1987) (noting that by the end of the nineteenth century, tort law “had assumed essentially its modern shape” in which the default standard of liability was negligence, and further elaborating on the role of contributory negligence within a negligence standard).

 [5]. See William K. Jones, Strict Liability for Hazardous Enterprise, 92 Colum. L. Rev. 1705, 1712 (1992).

 [6]. The prevalence of categories is a deep but manageable question, and it suggests the harder problem of justifying the placement of the negligence convention (and the convergence around it) far upstream in legal systems. The very development of a legal system, not to mention the establishment of a judiciary, can be placed yet further upstream. The characterization of rules and standards as either upstream or downstream is arguably a matter of taste and semantics, and it is not explored here; my claim about the descent from upstream to downstream, and from convergence to divergence, is more interesting than is identifying a starting point for, and the precise boundary of, convergence.

 [7]. See generally Merve Emre, The Personality Brokers: The Strange History of Myers-Briggs and the Birth of Personality Testing (2018) (describing the selling of the widely used Myers-Briggs personality test, replete with binary self-characterizations).

 [8]. Note that while I use public choice theory in explaining the binary character of many legal rules, this Article minimizes the role of public choice in developing rules and standards, and in bringing about convergence and divergence more generally. Powerful interest groups surely have great impact on law, and probably more on downstream than upstream decisions, but they hardly explain convergence and divergence quite generally. For example, something close to strict liability has become common for defective products, and that is hardly at the behest of well-organized interest groups. In other areas of law, like patents, powerful groups simply do not know in advance what rules will benefit them.

 [9]. See Saul Levmore, Rethinking Comparative Law: Variety and Uniformity in Ancient and Modern Tort Law, 61 Tul. L. Rev. 235, 235–87 (1986).

 [10]. This theory should be traced to Leo Katz, Why the Law Is So Perverse 6–7 (2011). On the implications for the binary quality of some law then developed, see generally Saul Levmore, Public Choice and Law’s Either/Or Inclination, 79 U. Chi. L. Rev. 1663 (2012) (reviewing Katz’s extraordinary book).

 [11]. See Henry M. Robert et al., Robert’s Rules of Order 425–28 (11th ed. 2011).

 [12]. I ignore remands, but these too will eventually lead to a binary decision if they are returned to an appellate court. Note that when a lower court determines damages or other results, these can be binary, but the decision is made by a single judge who is not subject to cycling, as discussed presently. See Judiciary Act of 1891, ch. 517, 26 Stat. 826, 829.

 [13]. See Duncan Black, On the Rationale of Group Decision-Making, 56 J. Pol. Econ. 23, 24 (1948).

 [14]. See William M. Landes & Richard A. Posner, The Positive Economic Theory of Tort Law, 15 Ga. L. Rev. 851, 919 (1981). As a matter of efficiency, the old approach was just fine, and indeed strict liability with a defense of contributory negligence was favored by some legal academics and economists. See, e.g., A. Mitchell Polinsky, Strict Liability vs. Negligence in a Market Setting, 70 Am. Econ. Rev. 363, 367 (1980); Richard A. Posner, Strict Liability: A Comment, 2 J. Legal Stud. 205, 207 (1973).

 [15]. Note the similarity to the divergence found in the law regarding the good-faith purchase of stolen property. Saul Levmore, Variety and Uniformity in the Treatment of the Good-Faith Purchaser, 16 J. Legal Stud. 43, 44–45 (1987).

 [16]. Inasmuch as a driver needs to meet the age requirement and also pass a driving test, the rules might be described as multifactor and not binary. But I will opt for binary because there is no chance that someone would prefer an underage driver who had failed the exam. There are two requirements, but little danger of cycling. Note that this argument assumes that it took years of experience before cycling became apparent and law therefore accommodated the shared ethical intuition in favor of comparative negligence. These evolutionary stories are plausible but sufficiently doubtful. As such, I do not want to make them a centerpiece of the theory offered here.

 [17]. See A. Chalmers Mole & Lyman P. Wilson, A Study of Comparative Negligence, 17 Cornell L. Rev. 333, 341–46 (1932). To be fair, there are situations in which a single decisionmaker can face something like a cycling problem, but this twist does not alter the present argument. See Katz, supra note 10, at 25–68.

 [18]. See Landes & Posner, supra note 14, at 919–20              . A related question is why change comes so slowly in some areas than in others. Why did American jurisdictions take so long to move to comparative negligence? One possibility is that judges felt free to sneak in comparative negligence by lowering damages within binary regimes. And, of course, in other areas of law where we now see convergence, U.S. law moved first.

 [19]. More detailed definitions of upstream and downstream—terms that are used rather loosely here—will emerge below. They are, inevitably, a matter of taste. “Upstream” laws are sometimes, but not always, those that pre-exist their downstream offspring; a legal system might decide to abandon contributory negligence, and then over time it might gravitate from one form of comparative negligence to another. More fundamentally, a system might install a legislature or judiciary and then be equipped to choose negligence or strict liability for wrongs done to others.

 [20]. This important example shows that the title of this Article can be misleading. The theory might better be titled “Convergence Where Efficiency and Shared Ethical Intuitions Are in Sync,” but this is less catchy and fails to suggest that we can explain divergence as well as convergence. In any event, in most areas of law, and certainly in most of tort law, the efficiency/ethical intuition match is found upstream.

 [21]. I could also include the choice between all-or-nothing and probabilistic-recovery rules. Ethical intuitions favor probabilistic recovery; a defendant who is found rather certainly to have caused a harm is commonly regarded as someone who should pay more for a given harm than one who is only 51 percent likely to have caused the injury or been negligent in doing so. There is, however, good reason to celebrate all-or-nothing directives as error-minimizing in most circumstances. I set this consideration aside both because I have addressed it in earlier work and because error minimization is not a synonym for efficiency. See Saul Levmore, Probabilistic Recoveries, Restitution, and Recurring Wrongs, 19 J. Legal Stud. 691, 692 (1990).

 [22]. See generally P.S. Atiyah, Tort Law and the Alternatives: Some Anglo-American Comparisons, 1987 Duke L.J. 1002 (noting variety in such areas as workers compensation, products liability, mass torts, and pain and suffering claims).

 [23]. Consider, for example, divergence in cases of products liability. While the United States and most European jurisdictions have adopted a strict liability approach, Canada has augmented the traditional negligence-based construction with additional remedies through contract. See Council Directive 85/374, 1985 O.J. (L 210) 29–33 (EC), amended by Directive 1999/34, 1999 O.J. (L 141) 20–21 (EC); David S. Morritt & Sonia L. Bjorkquist, Product Liability in Canada: Principles and Practice North of the Border, 27 Wm. Mitchell L. Rev. 177, 180–81 (2000).

 [24]. In general, civil law countries impose a “duty” to rescue. See, e.g., Edward A. Tomlinson, The French Experience with Duty to Rescue: A Dubious Case for Criminal Enforcement, 20 N.Y.L. Sch. J. Int’l & Comp. L. 451, 452 (2000). For example, both the French civil and criminal codes provide for a duty to rescue, with the criminal code prescribing five years’ imprisonment and a fine of 75,000 euros when individuals withhold aid from a person in danger which could be performed without risk to the rescuer or third parties. Code civil [C. civ.] [Civil Code] art. 1382 (Fr.); Code pénal [C. pén.] [Penal Code] art. 223-6 (Fr.). The Polish criminal code imposes a similar duty but limits it expressly to situations threatening an immediate danger of loss of life or serious bodily injury and imposes a penalty of up to three years’ imprisonment without an associated fine. Kodeks karny [K. K.] [Criminal Code] 1997, art. 162, sec. 1 (Pol.). The Argentine criminal code also limits liability, but bases its limitations on the identity of the would-be rescuer: specifically, it singles out those who “abandonado a su suerte” (“abandon to their fate”) an incapacitated individual in their care, or whom they have themselves incapacitated. Código Penal [Cód. Pen.] [Criminal Code] art. 106 (Arg.). The Argentine code imposes a sliding penalty of between two and fifteen years’ imprisonment based on the harm to the victim but joins Poland in foregoing additional civil penalties. Id. In sharp contrast to its civil law peers, the United States largely maintains that bystanders, though not caregivers or other singled-out parties, will not be liable for failures to rescue—joining in this respect other common law countries, including England. See Damien Schiff, Samaritans: Good, Bad and Ugly: A Comparative Law Analysis, 11 Roger Williams U. L. Rev. 77, 87 (2005); Marin Roger Scordato, Understanding the Absence of a Duty to Reasonably Rescue in American Tort Law, 82 Tul. L. Rev. 1447, 1452 (2008). On the other hand, it is common in U.S. jurisdictions to find liability for a failure to rescue when the would-be rescuer is in a “special relationship” with the one in need of rescue, as explained in the works cited in infra note 25. Thus Argentinian law, for instance, is not so different from judge-made laws in U.S. jurisdictions.

 [25]. See Saul Levmore, Waiting for Rescue: An Essay on the Evolution and Incentive Structure of the Law of Affirmative Obligations, 72 Va. L. Rev. 879, 881 (1986); see also Richard A. Epstein, A Theory of Strict Liability, 2 J. Legal Stud. 151, 190 (1973); Eric H. Grush, Note, The Inefficiency of the No-Duty-to-Rescue Rule and a Proposed “Similar Risk” Alternative, 146 U. Pa. L. Rev. 881, 883900 (1998); Richard L. Hasen, The Efficient Duty to Rescue, 15 Int’l Rev. L. Econ. 141, 141–42 (1995); Ernest J. Weinrib, The Case for a Duty to Rescue, 90 Yale L.J. 247, 269, 282 (1980).

 [26]. See Weinrib, supra note 25, at 279–93.

 [27]. See William M. Landes & Richard A. Posner, Salvors, Finders, Good Samaritans, and Other Rescuers: An Economic Study of Law and Altruism, 7 J. Legal Stud. 83, 119–28 (1978); Levmore, supra note 25, at 883–84.

 [28]. An objection to ex post selection of examples can of course be made to virtually all theorizing, whether in law or in medicine or any use of artificial intelligence. It is a danger that can only be overcome with more examples and with the promise that many of the examples offered here were chosen after the theory was stated.

 [29]. For example, substantial divergence has historically been present between United States’ and English jurisdictions, with the former choosing to hold children and the insane liable for tortious acts, and the latter denying their ability to be culpable in cases of tort. See Francis H. Bohlen, Liability in Tort of Infants and Insane Persons, 23 Mich. L. Rev. 9, 9–10 (1924). Still other jurisdictions, including Germany, Argentina, France, and Brazil, have adopted variations on the English view. See James W. Ellis, Tort Responsibility of Mentally Disabled Persons, 1981 Am. B. Found. Res. J. 1079, 1083.

 [30]. Eric Silver, Punishment or Treatment?: Comparing the Lengths of Confinement of Successful and Unsuccessful Insanity Defendants, 19 L. & Hum. Behav. 375, 377 (1995).

 [31]. See, e.g., A.R.H. v. W.H.S., 876 S.W.2d 687, 689 (Mo. Ct. App. 1994) (distinguishing verdicts following various claims of negligent supervision, in particular by weighing the ability of greater supervision to prevent harm); Kuhns v. Brugger, 135 A.2d 395, 401–02 (Pa. 1957) (describing the various considerations to be accounted for in determining juvenile negligence).

 [32]. Note that the definitions of upstream and downstream seem unobjectionable here. Upstream laws (or practices) are not necessarily earlier in time, but rather fundamental building blocks.

 [33]. See Saul Levmore & Ariel Porat, Threats and Criminal Deterrence in Several Dimensions, 2017 U. Ill. L. Rev. 1333, 1347–50. Nor is there reason to think that Artificial Intelligence will yield optimal prison sentences. See generally Saul Levmore & Frank Fagan, The Impact of Artificial Intelligence on Rules, Standards, and Judicial Discretion, 93 S. Cal. L. Rev. (forthcoming 2019).

 [34]. Some downstream divergence can be traced to a complete inability to know what a rule accomplishes. Thus, we are not surprised that there is divergence in religious beliefs or even in burial practices—and it is obvious that practitioners are unable to discern the efficiency (or after-life effects) of different rules.

 [35]. For an overview of electoral systems, and an analysis of the axioms driving their selection, see generally Pippa Norris, Choosing Electoral Systems: Proportional, Majoritarian and Mixed Systems, 18 Int’l Pol. Sci. Rev. 297 (1997).

 [36]. See generally Richard A. Epstein, How Spontaneous? How Regulated?: The Evolution of Property Rights Systems, 100 Iowa L. Rev. 2341 (2015) (discussing the relationship between spontaneous order and natural law).

 [37]. Levmore & Fagan, supra note 33.

 [38]. For Professor Tiebout’s seminal article on this hypothesis, see generally Charles M. Tiebout, A Pure Theory of Local Expenditures, 64 J. Pol. Econ. 416 (1956) (theorizing that individuals will move to communities with public goods provisions that suit their personal preferences and vice versa).

 [39]. See generally Saul Levmore, Interest Groups and the Durability of Law, in The Timing of Lawmaking 171 (Saul Levmore & Frank Fagan eds., 2017) (emphasizing lawmakers’ interest in appealing to a particular population’s preferences and doing so in a way that will last for some time).

 [40]. See Levmore & Fagan, supra note 33.