Private antitrust enforcement and the role of harmed parties in public enforcement

It is commonly believed that the possibility to sue privately for antitrust damages increases the probability that anticompetitive actions are prosecuted at the cost of an increased probability that procompetitive actions are prosecuted. We extend the analysis by taking into account that private parties often submit evidence during public investigation. Such parties consider private suit as a partial substitute for public prosecution. The trial option might induce these parties to be less willing to contribute evidence to public cases. Private trials crowd out public prosecution. In effect, the probability of prosecution of anticompetitive actions might decrease, while the earlier result that the probability of prosecuted actions being prosecuted is confirmed. In general, while the attractiveness of trials weakly decreases by considering a reporting possibility, they can remain an enforcement efficacy increasing institution.