مسئولیت 'علیت سازگار '، کارایی اقتصادی و قانون شبه جرم

Some legal scholars have argued that the standard modeling of liability rules is inconsistent with the causation requirement of the law of torts. It has been claimed that under the doctrinal notion of causation liability, an injurer is liable only if he was negligent. Moreover, he is liable for only that loss which can be attributed to his negligence and not the entire loss, as is the case with the standard modeling of liability rules. Our analysis shows that the ‘causation-consistent’ liability provides interesting insights on several issues concerning efficiency as well as compensation. Paper shows that when care is bilateral, causation-consistent liability provides a basis for efficiency characterization of the entire class of liability rules. Moreover, it remains a basis for the efficiency classification of liability rules even for bilateral-risk accidents.

In the standard modeling of liability rules, the proportion of accident loss a party is required to bear, generally, does not depend upon the extent to which the party contributed to the loss. For example, at the time of accident if the care level of an injurer was just below the due level of care, under the standard rule of negligence he is held liable for the entire loss. Moreover, a negligent injurer is held to be fully liable even when it can be established that at the time of accident the victim had taken no care at all. Similarly, under the rule of strict liability with the defense of contributory negligence, if the victim's care level falls just short of the due level, he would be liable for the entire accident loss irrespective of the level of care taken by the injurer. Some scholars have questioned this specification of liability rules ( Grady, 1983, Grady, 1988, Grady, 1989, Kahan, 1989, Wright, 1985 and Wright, 1987). In several scholarly writings, it has been argued that as a matter of legal doctrine, the standard modeling of liability rules is incorrect.1 Here, the argument is that under a liability rule, say the rule of negligence, the doctrinal notion of ‘causation liability’ has two requirements: (i) an injurer is liable only if he was negligent at the time of accident and (ii) a negligent injurer is liable for only the loss that can be attributed to his negligence. That is ‘causation liability’ restrict the liability of a negligent injurer to the part of accident loss that can be attributed only to the injurer's negligence. 2 For the ease of illustration, consider the following example. While engaging in his activity, a (potential) injurer can decide whether or not to take care. Let the cost of care be 1. If the injurer takes care the actual loss in the event of an accident will be 6, and 9 if he does not. The probability of an accident also depends upon the care level of the injurer, and is 1/3 when he takes care and 2/3 when he does not. Thus, when the injurer takes care, the expected loss is (1/3) × 6 = 2; while, if he does not take care, the expected loss is (2/3) × 9 = 6. Assume that the court will find the injurer negligent if and only if he does not take care. Under the standard modeling of the rule of negligence, liability of the negligent injurer is the entire loss, i.e. 9. As a result, the negligent injurer's expected liability is 2/3 × 9 = 6. But, note that the expected loss goes up only by 4 (i.e. 2/3 × 9–1/3 × 6) if the injurer does not take care. Therefore, under the standard rule of negligence, the expected liability of the negligent injurer is greater than the expected loss that can be attributed to his negligence. As an alternative, we can consider a liability assignment such that when the injurer is negligent his expected liability is only 4, i.e. equal to the increase in the expected loss caused by his negligence, not the entire expected loss. 3 This alternative specification of liability is what we call ‘causation-consistent’ liability, and forms the focus of the paper. Several noted legal scholars have advocated this alternative approach towards liability assignment. For instance, Honoré (1997) writes: “In a legal context, … when the enquiry concerns the causal relevance of wrongful conduct, as is usual in tort claims, we must substitute for the wrongful conduct of the defendant rightful conduct on his part. That is, when liability is based on fault, the comparison is not with what would have happened had the defendant done nothing, but what would have happened had he acted properly. … the aim of the legal enquiry is to discover not whether the defendant's conduct as such made a difference to the outcome, but whether the fact that it was wrongful did so.” (emphasis in the original). 4 In other words, under the standard modeling of the rule of negligence, when it comes to fixing the liability of a negligent injurer, the reference point is (the comparison is with) ‘what would have happened had the injurer done nothing.’ In contrast, under the causation-consistent liability, as our example illustrates, while determining the liability of a negligent injurer the reference point is his nonnegligent (rightful) act. The comparison is not with the situation in which he does not act at all. Note that in our example a compensation of 9 restores the victim to a position he would be in if there were no activity undertaken by the injurer and hence no accident. On the other hand, under the causation-consistent liability a victim will get compensation of only 6 (instead of 9). Very few analyses have formally dealt with this alternative specification of liability. The seminal work by Kahan (1989), and a more recent contribution by Van Wijck and Winters (2001) examine the efficiency implications of such specification of liability. The central message of these analyses is as follows: injurers take efficient care under the rule of negligence when the liability assignment is causation-consistent.5 These studies, however, have two drawbacks: (1) only the rule of negligence is considered, and (2) accidents are restricted to the unilateral-care case. On the first count, a liability rule may specify the due care only for the victim, or only for the injurer or may specify the due care levels for both the parties.6 If so, then for the rules that specify the due care for the victim, the causation doctrine can be extended to the negligence of the victim.7 On the second count, it should be noted that most accidents involve bilateral rather than unilateral care. This paper, in contrast to the above-mentioned works, studies the entire class of liability rules, and considers the bilateral-care accidents. We show that the ‘causation-consistent’ liability provides a basis for an efficiency characterization of the entire class of liability rules. Moreover, it remains a basis for an efficiency classification even when the risk is also bilateral. There is another literature to which this paper contributes. The economic analysis of liability rules has been undertaken by Brown (1973), Diamond (1974), Polinsky (1989), Landes and Posner (1987), Shavell (1987), Barnes and Stout (1992), Posner (1992), Levmore (1994), Kaplow (1995), Biggar (1995), Miceli (1997), Cooter and Ulen (2000), and Jain and Singh (2002), among others.8 These works show that if negligent injurers are made liable for the entire accident loss suffered by the nonnegligent victims, then injurers will be induced to take efficient care. We will show that liability for the entire loss is more than what is needed for efficiency; causation-consistent liability is sufficient. As our example shows, other factors remaining the same, the choice of care level by a party is likely to have different implications for the actual loss (that will materialize in the event of an accident) and the expected loss. One important question that arises is, ‘Should an injurer be considered as the ‘cause’ of the actual loss or of the expected loss when both can be attributed to his act?’ Calabresi (1970), Landes and Posner, 1983 and Landes and Posner, 1987, Shavell, 1985 and Shavell, 1987, Miceli, 1996 and Miceli, 1997, among others, have addressed this question. The basic proposition emerging from this work is that a party's action can raise or reduce the risk of harm, and therefore is a cause of the expected harm ( Ben-Shahar, 2000, Burrows, 1999, Cooter, 1987 and Miceli, 1997, pp. 22–24, Schwartz, 2000, pp. 1031–1033). 9 Depending upon the context, that is, the nature of the expected loss function, the expected accident loss that can be attributed to an injurer's negligence can be grater than, equal to, or less than his contribution to the actual loss. 10 Without imposing any significant restriction on the expected loss function, we show that a necessary condition for any liability rule to be efficient is to make a solely negligent injurer bear at least that fraction of the expected accident loss which can be attributed to his negligence. We introduce a condition called ‘causation liability’ that is consistent with the above-mentioned causation requirements. The condition of causation liability requires a liability rule to satisfy the following property: when the victim is nonnegligent, if the injurer chooses to be negligent rather than nonnegligent, then his expected liability will be more than his expected liability if he were just nonnegligent, by an amount that is at least the entire increase in the expected accident loss caused by his negligence. Similar rule applies for the victim. The first main result of the paper, Theorem 1, shows that if a liability rule satisfies this condition then it is efficient. Theorem 3, shows the necessity of the condition for efficiency of any liability rule. Our analysis shows that in at least one sense, rather than being contradictory, the above mentioned causation requirements turn out to be a necessary element for the efficiency of liability rules. As it turns out, the study of causation liability in addition to delineating the efficient liability rules from inefficient ones, can serve some important purposes. For example, with the set of all possible efficient liability rules in hand one can look for an efficient rule that ensures the maximum possible compensation to victims. Our analysis provides important insights on such issues. We also show that the rules that are efficient in the standard framework will still be efficient even when under these rules liability of a negligent party is reduced, as long as it is compatible with the above-mentioned requirements of causation. This paper captures yet another aspect of accidents. In reality many accidents involve bilateral-risk, that is, are such that both parties suffer losses in the event of an accident. Analysis in the paper covers bilateral-risk accidents as well. The existing results about the bilateral-risk accidents follow as a corollary to Theorem 4. Moreover, analogous to our results regarding unilateral-risk accidents, we show that for the purpose of economic efficiency it is not necessary that a solely negligent party bear all the losses suffered by both the parties, as is the case under the standard negligence-criterion based rules. Section 2 introduces the framework of analysis that outlines the notations and the assumptions made in the paper. Section 3 provides an efficiency characterization of efficient liability rules when, to start with, only one party bears accident losses, that is when risk is unilateral. In Section 4, we extend our analysis to cover bilateral-risk accidents. We conclude in Section 5 with remarks on the nature of framework and analysis in the paper.

In the literature on the law of torts, it is a well-established fact that when care is bilateral, the negligence or the due care criterion-based liability rules are efficient. These rules, as they are modeled in the economic analysis, have a common attribute: in the event of an accident, if one party is negligent and the other is not, then the negligent party is liable for the entire accident loss. This common feature of the negligence criterion-based liability rules causes a sudden jump in the liability of at least one party—for at least one party it is true that when the party reduces its care level from where it is not negligent to where it is negligent its liability jumps from no-liability to full-liability. Criticizing the standard modeling of liability rules, some (legal) scholars have argued that the above-mentioned drastic change in liability is not consistent with the causation doctrine of the law of torts. 25 From an efficiency point of view, our analysis ( Theorem 1 and Theorem 2) shows that a drastic change in liability is not necessary for economic efficiency; causation-consistent liability is sufficient to ensure efficiency. Theorem 3, shows that in at least one sense, causation-based liability is a necessary condition for any liability rule to be efficient. We have established similar results for the accident contexts that involve bilateral-risk. In particular, we have shown that for the purpose of economic efficiency, it is not necessary that a solely negligent party bear all the accident losses suffered by both the parties. This claim holds irrespective of whether the risk is unilateral or bilateral. Our enquiry into the efficiency implications of what we have called the causation-consistent liability throws up interesting research questions. These questions are relevant for the studies that have adopted an approach that is similar to ours. For example, when the liability assignment is ‘causation-consistent’ and care is unilateral, for the rule of negligence, Kahan (1989) and Van Wijck and Winters (2001) have proved two important results: (1) injurers opt for the efficient care level, and (2) the causation-consistent liability is superior to the conventional specification of liability in that the injurers’ care will still be efficient even when the legal standard of care is set at a higher (inefficient) level. Our analysis shows that the first claim can be extended to the bilateral-care accidents, and holds for all the negligence-criterion based liability rules. Whether the second claim holds in bilateral-care settings, and for other liability rules are the questions that need to be investigated. Future research studies might answer some of these questions. Earlier analyses of causation particularly by Grady and Kahan have argued that courts in fact apply the causation limit; but in the later analyses, it is argued that under the US tort law a negligent injurer is liable for the entire loss suffered by the victim. If so, causation-consistent liability is not a description of how the law of torts is practiced in courts. (But, note that though the condition CL does not insist on liability for the entire loss, full liability is not inconsistent with it.) We have shown that for economic efficiency, full liability is not necessary even when an injurer is solely negligent. Importance of the condition CL is underlined by the fact that it completely distinguishes the set of efficient liability rules, including those actually applied by courts and also other possible rules, from the rules that are not efficient. Finally a remark on the nature of the framework of analysis adopted in the paper. In the standard analyses it is generally taken that the cost of care is a continuous variable and the expected loss function is differentiable. But, Feldman and Frost (1998) have argued that the discrete and sometimes even dichotomous care is the reality of many accident settings. It should be noted that our modeling does not impose any condition and is more general than the standard modeling in this regard; it is equally applicable to both the continuous as well as the discrete variables. In addition, the liability rules considered in the paper are such that they satisfy the properties (P1) and (P2). Here, it is important to note that not only all the rules discussed in the literature satisfy these properties, as is shown in the discussion on Example 4, (P1) and (P2) have important efficiency implications.