Competition Among the Big and the Small


Many industries are made of a few big firms, which are able to manipulate the market outcome, and of a host of small businesses, each of which has a negligible impact on the market. We provide a general equilibrium framework that encapsulates both market structures. Due to the higher toughness of competition, the entry of big firms leads them to sell more through a market expansion effect generated by the shrinking of the monopolistically competitive fringe. Furthermore, social welfare increases with the number of big firms because the pro-competitive effect associated with entry dominates the resulting decrease in product diversity.


oligopoly, monopolistic competition, product differentiation, welfare

JEL Classification

L13, L40


Research Institute for Economics and Business Administration
Kobe University
Rokkodai-cho, Nada-ku, Kobe
657-8501 Japan
Phone: +81-78-803-7036
FAX: +81-78-803-7059

Jacques-François THISSE
CORE-Université catholique de Louvain (Belgium), CREA-Université du Luxembourg and CEPR