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In a Bertrand model of oligopoly, firms independently choose prices (not quantities) in order to maximize profits. This is accomplished by assuming that rivals' prices are taken as given. The resulting equilibrium is a Nash equilibrium in prices, referred to as a Bertrand (Nash) equilibrium.

When the industry is symmetric, i.e., comprising firms of equal size and identical costs, and the costs are constant and the product homogenous, the Bertrand equilibrium is such that each firm sets price equal to marginal cost, and the outcome is Pareto efficient. This result holds regardless of the number of firms and stands in contrast to the Cournot equilibrium where the deviation from Pareto efficiency increases as the number of firms decreases. However, when products are differentiated even the Bertrand model results in prices which exceed marginal cost, and the difference increases as products become more differentiated.

Source Publication:
Glossary of Industrial Organisation Economics and Competition Law, compiled by R. S. Khemani and D. M. Shapiro, commissioned by the Directorate for Financial, Fiscal and Enterprise Affairs, OECD, 1993.

Cross References:
Cournot (Nash) Equilibrium


Statistical Theme: Financial statistics

Created on Thursday, January 3, 2002

Last updated on Friday, February 28, 2003