In the context of an infinitely repeated capacity-constrained price game, we endogenize the composition of a cartel when firms are heterogeneous in their capacities. When firms are sufficiently patient, there exists a stable cartel involving the largest firms. A firm with sufficiently small capacity is not a member of any stable cartel. When a cartel is not all-inclusive, colluding firms set a price that serves as an umbrella with non-cartel members pricing below it and producing at capacity. Contrary to previous work, our results suggest that the most severe coordinated effects may come from mergers involving moderate-sized firms, rather than the largest or smallest firms. Copyright (c) 2010, RAND.

This note considers cartel stability when the cartelized products are vertically differentiated. If market shares are maintained at pre-collusive levels, then the firm with the lowest competitive price-cost margin has the strongest incentive to deviate from the collusive agreement. The lowest-quality supplier has the tightest incentive constraint when the difference in unit production costs is sufficiently small.

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This paper investigates the deterrent impact of anti-cartel enforcement. It is shown theoretically that if enforcement is effective in deterring and constraining cartels then there will be fewer cartels with low overcharges and fewer with high overcharges. This prediction provides an indirect method for testing whether the enforcement of competition law is effective. Using historical data on legal cartels to generate the counterfactual, we find significantly less mass in the tails of the overcharge distribution, compared to illegal cartels. This result is robust to controlling for confounding factors, and we interpret this as the first tentative confirmation of effective deterrence.