Collusion dans les enchères. Quelques apports des jeux coopératifs

We consider the second price sealed bid auction of an object that the potential buyers value privately and independently. We show that a cartel?s ex ante optimum, subject to incentive compatility and ex post balanced transfers, coincides with the first best and defines a supermodular characteristic function. By using two standard solution concepts, the core and the Shapley value, we show, among other properties, that every cartel is stable and that bidders gain in forming cartels whose size is as large as possible. We illustrate the difficulties to extend our results in the context of common values. Classification JEL : C71, D44.