A sequential equilibrium model of private antitrust enforcement is presented. Consumers have incomplete information about cartel costs and cannot accurately estimate a priori the damage recovery from an antitrust action. Consumers are able to infer cartel costs from the equilibrium pricing strategy of firms. The universal divinity criterion is used to characterize the sequential equilibrium. It is shown that, for a sufficiently large damage multiple, antitrust enforcement effectively increases social welfare. Copyright 1990 by American Economic Association.

A monopolist that sells in a market in which consumers differ in their willingness to pay for quality will distort and enlarge the range of products offered for sale. We examine the positive and normative impacts of remedies used to counteract such distortions. For the case of a price ceiling, the monopolist improves quality at the low quality end of the market, offsetting the distortion induced by the unregulated exercise of monopoly power. Social welfare can be shown to increase for a sufficiently slight degree of price regulation. For minimum quality standards, the social welfare implications are ambiguous because the standards may exclude some consumers from the market.