Tacit Collusion and Non–uniform Prices

This article examines the possibility of building a tacit agreement between price–setters that yields non–uniform pricing. It is shown that firms with market power may restrict competition not only by alternating between periods of high prices and low prices (Green and Porter (1984), Rotemberg and Saloner (1986)), but also by always charging different prices and taking turns in being the monopolist. In contrast with the existing literature, price variability is not due to imperfect monitoring, stochastic demand or short–run pricing rigidity but it is a pure supply side effect. The author provides the necessary conditions to have collusion with non–uniform pricing, and shows that the latter dominates a fixed price solution. In terms of competition policy this result confirms that no price parallelism is not, per se , a signal of no collusion.