This article identifies and then quantifies econometrically the impact of leniency programs on the perception of the effectiveness of antitrust policies in the business community using panel data for as many as 59 countries during a 14-year span. We use the dynamics of the gradual diffusion of leniency programs across countries and over time to evaluate the impact of the program, taking care of the bias caused by self-selection into the program. We find that leniency programs increase the perception of effectiveness by an order of magnitude ranging from 10 percent to 21 percent. Leniency programs have become weapons of mass dissuasion in the hands of antitrust enforcers against the more damaging forms of explicit collusion among rival firms in the market place.