THE MARKET SELECTS THE WRONG FIRMS IN THE LONG RUN*
研究自由进入如何影响非对称古诺寡头市场的结构和社会福利，发现长期中市场不仅可能选择错误的企业数量，还可能选择错误的企业类型。
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.