Endogenous market power

In this paper we develop a framework to study thin markets, in which all traders, buyers, and sellers are large, in the sense that they all have market power (also known as bilateral oligopoly). Unlike many IO models, our framework does not assume a priori that some traders have or do not have market power because “they are large or small.” Here, market power arises endogenously for each trader from market clearing and optimization by all agents. This framework allows for multiple goods and heterogeneous traders. We de…ne an equilibrium and show that such equilibrium exists in economies with smooth utility and cost functions and is determinate. The model suggests that price impact depends positively on the convexity of preferences or cost functions of the trading partners. In addition, the market power of di¤erent traders reinforces that of others. We also characterize an equilibrium outcome: Compared to the competitive model, the volume of trade is reduced and hence is Pareto ine¢ cient. JEL classification: D43, D52, L13, L14