When economists contemplate the invisible hand at work, they generally think of competitive markets. But there are some circumstances in which markets are not supposed to operate well (i.e., in which the invisible hand is thought to falter). A leading cause of market failure, many argue, is the presence of significant externalities. With such externalities, the first welfare theorem does not apply, and so competitive equilibrium-if it exists at all-is not typically Pareto optimal. In the tradition of A. C. Pigou (1932), the typical response to this lack of optimality is for the government to step in and introduce corrective policy, usually in the form of taxes or subsidies. There is, of course, a strong antiPigouvian tradition, as well. Specifically, proponents of the Coase theorem (Ronald Coase, 1960) have contended that, despite externalities, unrestrained bargaining and contracting ought to be sufficient to generate an efficient outcome. (Indeed Coase's own celebrated example was a case of externalities.) Thus, even if formal markets themselves fail, the invisible hand nevertheless succeeds, and outside intervention or design is not required. Recently, Joseph Farrell (1987) argued that, even when free bargaining is permitted, the laissez-faire conclusion inherent in the Coase theorem may founder if agents have incomplete information about one another's relevant characteristics. I shall show, however, that the problem that Farrell identified is due only to monopoly power and is not peculiar to externalities. Indeed, in this paper, I shall take a modified Coasian stance. I shall attempt to show that, in spite of externalities and incomplete information, private contractual agreements suffice to achieve efficiency, as long as no agent is big enough to have significant market power. This conclusion must be qualified, however, with the proviso that, if the externality is (i.e., no one can be excluded from its effects), the government must intervene to prevent free-riding on the agreements. Intervention, in this case, amounts to establishing the right of an agent providing a positive external effect to collect a fee for increasing the effect from all who enjoy it, even if they are not parties to a contract with the provider. Symmetrically, providers of a negative externality can collect a fee for diminishing the effect from all their victims. In either case, however, the fee is set endogenously, that is, it is determined by the contractual arrangements rather than by the government. This result for nonexcludable externalities (which include pure public goods) provides support for a fairly laissez-faire stance toward externalities but turns on an important assumption, namely, that parties always write contracts so as to maximize their social surplus (subject to incentive and individual-rationality constraints). I will return to this assumption in the final section.

We scrutinize the conceptual framework commonly used in the incomplete contract literature. This literature usually assumes that contractual incompleteness is due to the transaction costs of describing—or of even foreseeing—the possible states of nature in advance. We argue, however, that such transaction costs need not interfere with optimal contracting (i.e. transaction costs need not be relevant), provided that agents can probabilistically forecast their possible future payoffs (even if other aspects of the state of the nature cannot be forecast). In other words, all that is required for optimality is that agents be able to perform dynamic programming, an assumption always invoked by the incomplete contract literature. The foregoing optimality result holds very generally provided that parties can commit themselves not to renegotiate. Moreover, we point out that renegotiation may be hard to reconcile with a framework that otherwise presumes perfect rationality. However, even if renegotiation is allowed, the result still remains valid provided that parties are risk averse.

We first point out that the recent property-rights literature is based on three assumptions: (1) that contracts are always subject to renegotiation; (2) that the exercise of a property right confers a private benefit and (3) that parties are risk-neutral. Building on Hart-Moore (1999), we provide conditions under which an optimal contract consists of nothing more than an assignment of property rights. We also examine the robustness of some of the literature's standard predictions about asset ownership to the introduction of mechanisms for eliciting parties' ex post willingness to pay for the assets (such as options or financial markets). To illustrate the issue, we revisit the Hart-Moore (1990) proposition that joint ownership is suboptimal, and argue that ownership by a single party is dominated by joint ownership with put options.

The paper characterizes the choice rules that can be implemented when agents are unable to commit themselves not to renegotiate the mechanism.

Partha Dasgupta, Eric Maskin; The Existence of Equilibrium in Discontinuous Economic Games, II: Applications, The Review of Economic Studies, Volume 53, Is

Partha Dasgupta, Eric Maskin; The Existence of Equilibrium in Discontinuous Economic Games, I: Theory, The Review of Economic Studies, Volume 53, Issue 1, 1 Jan

A principal has private information that directly affects her agent's payoff (i.e., "common values" obtains). The authors analyze their relationship as a three-stage game: (1) the principal proposes a contract; (2) the agent accepts or rejects; and (3) the contract is executed. They show that the equilibrium outcomes are the allocations that weakly Pareto dominate the allocation maximizing the payoff of each "type" of the principal within the class of incentive-compatible allocations ensuring the agent his reservation utility irrespective of his beliefs about the principal's type. The authors also characterize the equilibria that are immune to renegotiation. Copyright 1992 by The Econometric Society.

The authors analyze the principal-agent relationship when the principal has private information as a three-stage game: contract proposal, acceptance/refusal, and contract execution. They assume that the information does not directly affect the agent's payoff (private values). Equilibrium exists and is generically locally unique. Moreover, it is Pareto optimal for the different types of principal. The principal generically does strictly better than when the agent knows her information. Equilibrium allocations are the Walrasian equilibria of an "economy" where the traders are different types of principal and "exchange" the slack on the agent's individual rationality and incentive compatibility constraints. Copyright 1990 by The Econometric Society.

The authors provide game theoretic foundations for the classic kinke d demand curve and Edgeworth cycle. In their alternating-move model, there are multiple Markov perfect equilibria of both the kinked deman d curve and Edgeworth cycle variety. In any Markov perfect equilibria , profit is bounded away from the Bertrand equilibria level. A kinked demand curve at the monopoly price is the unique symmetric "renegot iation proof" equilibrium when there is little discounting. The auth ors then endogenize the timing by allowing firms to move at any time. They find that firms end up alternating, thus vindicating the fixed timing assumption of the simpler model. Copyright 1988 by The Econometric Society.