[A model of decentralized exchange and price formation is defined using the bargaining theory of A. Rubinstein. Agents meet at random and bargain over the terms of trade. If there are no transaction costs, every perfect equilibrium of the bargaining game implements a Walrasian equilibrium of the underlying exchange economy.]

Extensive-form market games typically have a large number of noncompetitive equilibria. In this paper, we argue that the complexity of noncompetitive behavior provides a justification for competitive equilibrium in the sense that if rational agents have an aversion to complexity (at the margin), then maximizing behavior will result in simple behavioral rules and hence in a competitive outcome. For this purpose, we use a class of extensive-form dynamic matching and bargaining games with a finite number of agents. In particular, we consider markets with heterogeneous buyers and sellers and deterministic, exogenous, sequential matching rules, although the results can be extended to other matching processes. If the complexity costs of implementing strategies enter players’ preferences lexicographically with the standard payoff, then every equilibrium strategy profile induces a competitive outcome.

The authors characterize the symmetric equilibria of an investment game with a pure informational externality. When the period length is very short, the game ends very quickly; with positive probability, an informational cascade (herding) causes an investment collapse. As the period length increases, the possibility of herding disappears. As the number of players increases, the rate of investment and the information flow are eventually independent of the number of players; adding more players simply increases the number who delay. In the limit, a period of low investment is followed by either an investment surge or a collapse. Copyright 1994 by The Econometric Society.

A complex financial system comprises both financial markets and financial intermediaries. We distinguish financial intermediaries according to whether they issue complete contingent contracts or incomplete contracts. Intermediaries such as banks that issue incomplete con-tracts, e.g., demand deposits, are subject to runs, but this does not imply a market failure. A sophisticated financial system–a system with complete markets for aggregate risk and limited market participation–is incentive-efficient, if the intermediaries issue complete con-tingent contracts, or else constrained-efficient, if they issue incomplete contracts. We argue that there may be a role for regulating liquidity provision in an economy in which markets for aggregate risks are incomplete. 1 Markets, intermediaries and crises For a long time, it has been taken as axiomatic that financial crises are best avoided. We confront this conventional wisdom by showing that, under certain conditions, a laisser-faire financial system achieves the incentive-efficient or constrained-efficient allocation.1 Further-more, constrained efficiency may require financial crises in equilibrium. The assumptions

The authors describe a model of general equilibrium with incomplete markets in which firms can innovate by issuing arbitrary, costly securities. When short sales are prohibited, firms behave competitively and equilibrium is efficient. When short sales are allowed, these classical properties may fail. If unlimited short sales are allowed, imperfect competition may persist even when the number of potential innovators is large. If limited short sales are allowed, perfect competition may obtain in the limit, but equilibrium can be inefficient because of the presence of an externality: the private benefits of innovation for firms differ from the social benefits. Copyright 1991 by The Econometric Society.