Comparative Causation


As Calabresi (1996) pointed out, no consideration has been given in recent legal and economic literature to the idea of distributing an accident loss among a faultless tortfeasor and an innocent victim on the basis of the relative causal contribution of the parties to the loss. This criterion of apportionment of liability, which we call "comparative causation," is the object of this paper. We present a brief intellectual history of the principle of comparative causation and provide a positive economic model. In order to identify structural features of the rule, we first consider a rule of pure comparative causation where liability is allocated on the basis of causation, regardless of parties' fault. The economic model brings to light some interesting features of the rule, but also unveils the limits of such a criterion of liability with respect to induced activity and care levels. The paper then extends the economic model to consider the workings of the comparative causation rule in conjunction with negligence rules. Applying the comparative causation rule under a negligence regime induces a combination of incentives that no known liability rule provides.