THE MARKET SELECTS THE WRONG FIRMS IN THE LONG RUN *

We consider the effects of free entry on the market structure and social welfare of an asymmetric Cournot oligopoly. Even if we allow for the existence of different types of firms initially, only one type (in almost all cases) can survive in the long run. Free entry leads an economy to a symmetric equilibrium, in which the excess entry theorem holds. Further, we consider the socially optimal policy for this economy. In cases of either (i) a concave demand (which implies strategic substitutability) or (ii) strategic complementarity (which implies a convex demand), the type of firms that should remain in the market to achieve social optimality does not necessarily coincide with the type of firms that will survive in the long run. The market may select not only the wrong number of firms but also the wrong type of firms in the long run. Copyright 2005 by the Economics Department Of The University Of Pennsylvania And Osaka University Institute Of Social And Economic Research Association.