[The meaning of exchange efficiency is examined in the context of an economy in which agents differ in their endowments of information. Definitions of efficiency, and of the core, are proposed which emphasize the role of communication. Opportunities for insurance are preserved by restricting communication, or in a market system by restricting insider trading, prior to the pooling of information for the purposes of production.]

[In this paper the process of exchange is formulated as a noncooperative game. The game is analogous to the familiar institution of competitive bidding in a sealed-tender auction in which one agent (the auctioneer) chooses among trades offered by the other agents (the bidders). Using various regularity assumptions it is shown that this noncooperative game has a Nash equilibrium which yields an allocation in the core of the corresponding cooperative game of exchange. Also, as the bidders are replicated by division this allocation (aggregated by types) converges to a Walrasian allocation in which each type's budget constraint (using the efficiency prices) is satisfied. Thus it appears that bidding is a competitive process for achieving a cooperative outcome, and in the limit, a market outcome.]

[A parametric procedure for linear programming is shown to solve the bilinear complementarity problem, of which a special case is the problem of computing a competitive equilibrium of a piecewise linear economic model.]