In a discretionary regime the monetary authority can print more money and create more inflation than people expect. But, although these inflation surprises can have some benefits, they cannot arise systematically in equilibrium when people understand the policymakor's incentives and form their expectations accordingly. Because the policymaker has the power to create inflation shocks ex post, the equilibrium growth rates of money and prices turn out to be higher than otherwise. Therefore, enforced commitments (rules) for monetary behavior can improve matters. Given the repeated interaction between the policymaker and the private agents, it is possible that reputational forces can substitute for formal rules. Here, we develop an example of a reputational equilibrium where the outcomes turn out to be weighted averages of those from discretion and those from the ideal rule. In particular, the rates of inflation and monetary growth look more like those under discretion when the discount rate is high.

Economists have long been ambivalent about whether the discipline should focus on the analysis of markets or should be concerned with social interactions more generally. Recently the discipline has sought to broaden its scope while maintaining the rigor of modern economic analysis. Major theoretical developments in game theory, the economics of the family, and endogenous growth theory have taken place. Economists have also performed new empirical research on social interactions, but the empirical literature does not show progress comparable to that achieved in economic theory. This paper examines why and discusses how economists might make sustained contributions to the empirical analysis of social interactions.

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We consider the problems of societal norms for cooperation and reputation when it is possible to obtain "cheap pseudonyms", something which is becoming quite common in a wide variety of interactions on the Internet. This introduces opportunities to misbehave without paying reputational consequences. A large degree of cooperation can still emerge, through a convention in which newcomers "pay their dues" by accepting poor treatment from players who have established positive reputations. One might hope for an open society where newcomers are treated well, but there is an inherent social cost in making the spread of reputations optional. We prove that no equilibrium can sustain significantly more cooperation than the dues-paying equilibrium in a repeated random matching game with a large number of players in which players have finite lives and the ability to change their identities, and there is a small but nonvanishing probability of mistakes. Although one could remove the ineffici...

This paper develops a positive theory of credibility, ambiguity, and inflation under discretion and asymmetric information. The monetary policymaker maximizes his own (politically motivated) objective function that is positively related to economic stimulation through monetary surprises and negatively related to monetary growth. The relative import-ance he assigns to each target shifts stochastically through time. His current preference trade-off is known to him but not to the public. When choosing the (state contingent) path of money growth for the present and the future, the policymaker compares the benefits from current stimulation with the costs associated with higher future inflation expectations. Current monetary growth conveys information to the public about future money growth because there is persistence in the policymaker's objectives. Although expectations are rational, information is imperfect because monetary control procedures are imprecise. As a result the public cannot correctly distinguish persistent changes of emphasis on different policy objectives from transitory monetary control errors. The public becomes aware of changes gradually by.observing past monetary growth. Credibility is defined in terms of the speed with which the public recognizes changes in the objectives of the policymaker.

Standard incentive theory models provide a rich framework for studying informational problems but assume that contracts can be perfectly enforced. This paper studies the design of self-enforced relational contracts. I show that optimal contracts often can take a simple stationary form, but that self-enforcement restricts promised compensation and affects incentive provision. With hidden information, it may be optimal for an agent to supply the same inefficient effort regardless of cost conditions. With moral hazard, optimal contracts involve just two levels of compensation. This is true even if performance measures are subjective, in which case optimal contracts terminate following poor performance.

The authors have benefitted from discussions with Rao Aiyagari as well as from seminars at Harvard and Indiana Universities. The views expressed in this paper are those of the authors and do not necessarily represent the views of the Board of Governors of the Federal Reserve System. Financial support from the Alfred P. Sloan Foundation is gratefully acknowledged. The research reported here is part of the NBER's research program-in Economic Fluctuations. Any opinions expressed are those of the authors and not those of the

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pp. 428–465 We analyze collusion in an infinitely repeated Bertrand game, where prices are publicly observed and each firm receives a privately observed, i.i.d. cost shock in each period. Productive efficiency is possible only if high-cost firms relinquish market share. In the most profitable collusive schemes, firms implement productive efficiency, and high-cost firms are favored with higher expected market share in future periods. If types are discrete, there exists a discount factor strictly less than one above which first-best profits can be attained using history-dependent reallocation of market share between equally efficient firms. We also analyze the role of communication and side-payments. 1.