Hopkins, 548 S.W.2d 344 (Text 1977). The effect was to reduce the plaintiff's judgment rendered under strict liability in proportion to the causal contribution of the plaintiff's "unforseeable misuse." The goal was to circumvent the "apples and oranges" problem of comparing fault with strict liability. The concept is discussed in Aaron D. Twerski, The Many Faces of Misuse: An Inquiry into the Emerging Doctrine of Comparative Causation, 29 MERCER L. REV. 403 (1978).
Other writers have sought to develop a general theory of casual apportionment for tort eases. See Mario J. Rizzo & Frank S. Arnold, Casual Apportionment in the Law of Torts: An Economic Theory, 80 COLUM. L. REV. 1398 (1980). These authors employ the concept of "probalistic marginal product" (PMP) to develop a "technology" that assigns damage shares in simultaneous cause cases "by measuring the differential degree of risk to which each cause exposes the plaintiff." Id. at 1408. The authors found their inspiration for developing this method in Richard A. Epstein, A Theory of Strict Liability, 2 J. LEGAL STUD. 151 (1973), in which Professor Epstein calls for the return to a tort system based solely on causation; if A causes harm to B, A should compensate B without inquiry into questions of fault. Although Rizzo and Arnold buy into the simpler rules of Epstein's strict liability world, they claim their technology can also be used to apportion damages among tortfeasors whose conduct has been found to be negligent.
Rizzo and Arnold's technology was criticized in David Kaye & Mikel Aickin, A Comment on Causal Apportionment, 13 J. LEGAL STUD. 191 (1984), which was later followed by a vigorous defense in Mario J. Rizzo & Frank S. Arnold, Causal Apportionment: Reply to the Critics, 15 J. LEGAL STUD. 219 (1986). Without taking sides on the technical aspects of the dispute, we think Kaye and Aicken raise relevant issues when they state, "We think it is fair to ask for some proof that this form of contribution [based on probalistic marginal product] would create the proper incentives for optimal levels of care on the part of each joint tortfeasor." Kaye & Aicken, supra, at 205. They note that Rizzo and Arnold "do not place much weight on efficiency," id., and conclude that, while strict liability may have some claim to greater efficiency over negligence in the absence of administrative and transaction costs, the causal apportionment formula does entail such costs so "that this form of apportionment ... seems difficult to defend on efficiency grounds." Id. With respect to fairness, they state, "it would not follow that apportionment according to some function of the PMPs is the fairest way to impose damages. As far as we can tell, there is no uniquely meaningful or manifestly fairest way to compute the relative contributions of two causes to an indivisible injury." Id. at 206.
(n194) We agree that the probalistic marginal product (PMP), see supra note 193, is an inadequate concept for apportionment because it ignores the egregiousness of the tortfeasor's conduct and the relative stakes the tortfeasors have in the enterprises to which they have contributed their wrongful conduct. On the other hand, we think that the magnitude of each party's contribution to the risk of the indivisible injury is one of the factors to be weighed in reaching a culpability apportionment ratio. If PMP analysis can provide a principled way to derive these magnitudes that is superior to asking the trier of fact in essence to use its intuitive good sense, then we support the concept as being a useful tool for damage apportionment under a negligence regime. We believe, however, that when the weighing of the quantitative production of risk by the various parties is accompanied by weighing egregiousness and the relative stakes