A market with asymmetric information

This chapter discusses an equilibrium concept that differs from the notions of competitive equilibrium discussed in Chapters 9–12. The models in the earlier chapters specify the precise set of economic agents who operate in the market, and an equilibrium specifies the terms of trade (prices) for which the aggregate demand and supply of these agents are equal. The model we study in this chapter does not explicitly specify the set of agents. As a consequence, the equilibrium notion is more abstract. A set of contracts is an equilibrium if no agent who offers a contract wants to withdraw it, and no agent can profit by adding a contract.

We illustrate the concept by applying it to a model central to the economics of information. The problems at the end of the chapter demonstrate the use of the concept to study other economic interactions.