La thèse d'efficience du « théorème de Coase ». Quelle critique de la microéconomie ?

The efficiency claim of the ?Coase theorem? harshly criticises welfare economics: it asserts that an optimal result will be reached, even in the presence of externalities. However, the precise meaning of this criticism depends on the nature of the exchange. If the ?theorem? assumes perfect competition, it widens the conclusion of the first welfare theorem to externalities. If, as it is more likely, it assumes decentralized negotiations, it concludes that a bilateral bargaining over property rights is efficient if transaction costs are zero. In this case, the heavy assumptions of the perfect competition model would not be necessary. The question of the meaning of the zero transaction costs assumption is raised in this frame. Classification JEL : B21, C78, D62.