 A second economic account, introduced by Richard Posner, analyzes the efficiency problem of safety differently. On this view, the negligence standard is the appropriate tool to ensure that people neither overinvest nor underinvest in safety (Posner 1972). Economically rational agents will not overinvest in safety because they will not assume expenses from which they expect no return. Underinvestment in safety is a potential problem, and so the key to an efficient level of investment in safety is to provide those imposing risks with the right incentive to reduce them. The appropriate level is set by making injurers bear the cost of excessive risks that they impose. A specific risk counts as excessive if the cost of reducing it is less than the expected cost—the seriousness of the injury discounted by its likelihood—of allowing it to occur. If the burden of precaution costs is greater than the discounted cost of the injury, then it is economically rational for the law to permit the defendant to impose the risk. If someone is injured because it was not efficient to take a precaution, the injurer should not be held liable; provided that the level of precaution taken was economically efficient, transferring funds from the injurer to the injured party is merely redistributive, and does not improve the overall social allocation of resources. Posner contends that the only point of tort liability is to provide incentives for optimal investment in safety; the fact that the defendant pays the plaintiff in particular is incidental to the account. Instead, Posner suggests that the plaintiff receives payment exclusively as an incentive to bring the lawsuit; in effect the plaintiff serves as a kind of private attorney general. The role of the plaintiff in Posner’s analysis tracks the role of the plaintiff in the standard economic analysis of US antitrust law, in which damages are awarded to plaintiffs to incentivize them to bring suits without those plaintiffs having been specially affected by the pervasive negative consequences of anticompetitive behavior.