The Welfare Effects of Third-Degree PriceDiscrimination in a Differentiated Oligopoly

This paper studies the welfare effects of third-degree price discrimination under oligopolistic competition with horizontal product differentiation. We derive a necessary and sufficient condition for price discrimination to improve social welfare: the degree of substitution must be sufficiently greater in the "strong" market (where the discriminatory price is higher than the uniform price) than in the "weak" market (where it is lower). It is verified, however, that consumer surplus is never improved; social welfare improves solely due to an increase in the firms' profits.