Apportionment rules in case of several tortfeasors : an interdisciplinary approach – DAMAGE

The originality of DAMAGE proposal relies on different levels

First, we analyze causation in law thanks to counterfactual theories of causation. Counterfactual theories are well-known in social sciences in general (history for example or economics) but they are not used in legal fields while they are close to the jurisdiction reasoning.
Second, we propose to apply cooperative game theory to multiple causation games. Contrary to traditional law and economics models (see State of the art) which only use non-cooperative game theory, our approach is to modeling the issue as a sharing cost game. This approach is fruitful insofar as the deep roots of the issue is to know how sharing a payment between several individuals. We would try to characterize different solution-rules thanks to an axiomatic approach. According to us, axiomatic allows to organize law and economics on solid analytic grounds.
Third, we propose to constitute an original data set on this topic which is quite rare in France. This data set will be constituted by decisions from Supreme civil Court and Appeal courts. The aim is to know whether the decisions of French courts may be analyzed thanks to the axiomatic rules. It will be then possible to compare French solutions to decisions done in other countries.
The expected results from our proposal are: 1/ Providing a general economic approach of the multiple causation and sharing issue, 2/ Applying this approach to courts decisions in France, 3/ Comparing French practices with other practices in foreign countries.

The main results of our research have been to identify the economic properties of different sharing rules in case of multiple causation litigation. We elaborate these result thanks to a typology of the different possible cases: simultaneous causation, sequential causation, victim's fault and alternative causation. The purely simultaneous case is the most difficult because of the amount of information needed to solve the game with an axiomatic approach
Our research agenda has been to study different fileds of law (medical malpractice, class actions, accident law, antitrust damages) and to show their deep structures in terms of axiomatics.

The perspectives of our research are now to make an empirical analysis of the French litigation. Thanks to the collaboration with the French Supreme Civil Court, we have an access to the data base «Jurica« which is an exhaustive data base on French Courts of Appeal decisions. Our aim is now to anlyse this data base and to explore the principles used in practices by courts to solve such litigations. More precisely, we will test our theoretical approach to know wether Courts decision could be rationalized on axiomatic grounds or not. Then it will be possible to provide to pratitionners a comprehensive view on what's going on in France about multiple causation litigations.

Published and forthcoming papers

P. Dehez et S. Ferey (2013), « How to Share Joint Liability. A Cooperative Game Approach », Mathematical Social Sciences, vol. 66, n°1, pp. 44-50.

S. Ferey (2013), « Dommages punitifs, dissuasion et punition en économie du droit : quelques résultats et paradoxes », Revue Lamy droit des affaires, n°85, sept., pp. 112-116.
F. G’Sell et S. Ferey (2013), « Pour une prise en compte des parts de marché dans la détermination de la contribution à la dette de réparation », Recueil Dalloz, n°41, novembre, pp. 2709-2712.
S. Ferey (2015), « Causalité et répartition des dommages par de multiples co-auteurs : une approche par la théorie des jeux coopératifs », Économie et Prévisions, à paraître.
M. Doriat-Duban, S. Harnay et S. Ferey, (2015), « Class action, Incentives and Apportionment : an Economic Perspective » in Class action in Europe (ss dir. de D. Fairgrieve)

Revised Papers
P. Dehez et S. Ferey, « Apportionment and The Shapley Value », en revision.
M. Deschamps et S. Beal, « On compensation schemes for data sharing within the European REACH legislation », en revision.


Conférences internationales
Congrès « philosophie et économie », Strasbourg, octobre 2014 ; Congrès de l’association asiatique d’économie du droit (Asian Law and Economics Association), Taipei, juin, 2014 ; Congrès de la société canadienne de Sciences Economiques, Ottawa, mai 2014 ; Congrès de l’association allemande d’économie du droit (German Law and Economics Association), Bolzano, septembre 2013; Journées en la mémoire de Jean-François Mertens, Jérusalem (organisé par le Core, Louvain), juin 2013,

Organisation de conférences
Colloque de mi-parcours « Causalité, Responsabilité et Répartition » organisé à la Cour de cassation, 12-13 septembre 2014.
Session spéciale organisée au colloque de philosophie économique, « Causation and Responsibility » Strasbourg, octobre 2014

Sharing a damage that has been caused by several individuals is a difficult problem that courts often face. Even if there exist basic principles and rules to apportion damages among them (like for instance in the third Restatement of Torts promulgated in May 1999 for the United-States), legal scholars are still looking for a systematic method. Many examples of such litigation come to mind: a car driver hurts a pedestrian and breaks his or her leg. Then, the victim is taken to a hospital to be looked after but, because of the fault of the surgeon, he or she completely loses the use of his or her leg and gets amputated. Apportionment rule is needed to correctly share the damage paid by each tortfeasors. Such litigations occur as soon as two or more individuals have jointly caused damages and it is easy to think about the different fields of law concerned by this issue: environmental law and nuisance, accident law, medical malpractices, products liability, victim contributions, securities law, antitrust etc.
The aim of the paper is to reconsider the issue of apportionment among multiple tortfeasors to expose some economic principles which could be applied by the judiciary in order to rationally share the damages due by each tortfeasor. But contrary to many models in law and economics, we do not use a non-cooperative game approach. In the following, damage is modeled as a cooperative game where different agents – the tortfeasors – jointly create an indivisible economic loss, the damage.
The DAMAGE project aims at showing how the cooperative approach may bring useful insights into legal questions. The main issue we address in this project is the following. We use cooperative game approach as a model to evaluate the causal role of each tortfeasor. Our aim is to build a set of structured games which fit with the main cases of multiple causation (successive injury, victim’s fault, joint damage etc.) and to solve these games with usual solution concepts used in cooperative game theory. Then we will study the consequences of such apportion rules on the incentives followed by the tortfeasors.
This main issue leads to two others issues. The first one is to know whether cooperative game approach is consistent with contemporary counterfactual theories of causation. The second one is to study whether the French jurisdictions practices (mainly civil courts) are enlightened by our approach. We will proceed to an empirical study by building an original data set on the main French courts decisions on this topic. And this date base will finally be open to legal scholars, judges and lawyers.