An antitrust authority deters collusion using fines and a leniency program. It chooses the probability of an investigation. Firms pick the degree of collusion: The more they collude, the higher are profits, but so is the probability of detection. Firms thus trade-off higher profits against...

Leniency programs lower the expected cost of anticompetitive behavior to the extent that they allow colluding firms to pay reduced fines. This paper connects this potential adverse effect to the number of firms involved in the cartel agreement. It is shown that leniency programs may provide...