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.

We study industries where the price that a firm sets serves as an investment into lower cost or higher demand. We assess the welfare implications of the ensuing competition for the market using analytical and numerical approaches to compare the equilibria of a learning-by-doing model to the first-best planner solution. We show that dynamic competition leads to low deadweight loss. This cannot be attributed to similarity between the equilibria and the planner solution. Instead, we show how learning-by-doing causes the various contributions to deadweight loss to either be small or partly offset each other.

We formally characterize predatory pricing in a modern industry-dynamics framework that endogenizes competitive advantage and industry structure. As an illustrative example we focus on learning-by-doing. To disentangle predatory pricing from mere competition for efficiency on a learning curve we decompose the equilibrium pricing condition. We show that forcing firms to ignore the predatory incentives in setting their prices can have a large impact and that this impact stems from eliminating equilibria with predation-like behavior. Along with the predation-like behavior, however, a fair amount of competition for the market is eliminated.

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.