This paper reports results from an experiment studying how …nes, leniency and rewards for whistleblowers a¤ect cartel formation and prices. Antitrust without leniency reduces cartel formation but increases cartel prices: subjects use costly …nes as punishments. Leniency improves antitrust by strengthening deterrence but stabilizes surviving cartels: subjects appear to anticipate the lower post-conviction prices after reports/leniency. With rewards, prices fall at the competitive level.Overall our results suggest a strong cartel deterrence potential for well-run leniency and reward schemes. These …ndings may also be relevant for similar white-collar organized crimes, like corruption and fraud.JEL codes: C73, C92 and L41

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This paper presents results from a laboratory experiment studying the channels through which different law enforcement strategies deter cartel formation. With leniency policies offering immunity to the first reporting party, a high fine is the main determinant of deterrence, having a strong effect even when the probability of exogenous detection is zero. Deterrence appears to be mainly driven by 'distrust'; here, the fear of partners deviating and reporting. Absent leniency, the probability of detection and the expected fine matter more, and low fines are exploited to punish defections. The results appear relevant to several other forms of crimes that share cartels' strategic features, including corruption and financial fraud.

Many commodities (including energy, agricultural products and metals) are sold both on spot markets and through long-term contracts which commit the parties to exchange the commodity in each of a number of spot market periods. This paper shows how the length of contracts affects the possibility of collusion in a repeated price-setting game. Contracts can both help and hinder collusion, because they reduce the size of the spot market, cutting both the immediate gain from defection and the punishment for deviation. Firms can always sustain some collusive price above marginal cost if they sell the right number of contracts, of any duration, whatever their discount factor. As the duration of contracts increases, however, collusion becomes harder to sustain.