Coalitional Bayesian Nash implementation in differential information economies

Summary. A mechanism coalitionally implements a social choice set if any outcome of the social choice set can be achieved as a coalitional Bayesian Nash equilibrium of a mechanism and vice versa. We say that a social choice set is coalitionally implementable if there is a mechanism which coalitionally implements it. Our main theorem proves that a social choice set is coalitionally implementable if and only if it is interim individually rational, interim efficient, coalitional B ayesian incentive compatible, and satisfies a coalitional Bayesian monotonicity condition as well as a closure condition. As an application of our main result, we show that the private core and the private Shapley value of an economy with differential information are coalitionally implementable. Received: January 12, 1998; revised version: March 30, 2000     

Belief-Based Equilibria in the Repeated Prisoners' Dilemma with Private Monitoring

We analyze repeated prisoners' dilemma games with imperfect private monitoring and construct mixed trigger strategy equilibria. Such strategies have a simple representation, where a player's action only depends upon her belief that her opponent(s) are continuing to cooperate. When monitoring is almost perfect, the symmetric efficient outcome can be approximated in any prisoners' dilemma game, while every individually rational feasible payoff can be approximated in a class of such games. The efficiency result extends when there are more than two players. It requires that monitoring be sufficiently accurate but does not require very low discounting when a public randomization device is available. Journal of Economic Literature Classification Numbers: C73, D82.     

MONEY AS A MECHANISM IN A BEWLEY ECONOMY*

We investigate the efficiency property of a monetary economy with spot trade. We prove a conjecture that is essentially due to Bewley (Models of Monetary Economics (1980); Econometrica 51 (1983), 1485–504). The gist is that monetary spot trading is nearly efficient ex ante in an environment where very patient agents can accumulate large enough money stocks to be completely self‐insured. We also study examples where a nonmonetary mechanism is preferred ex ante to any monetary mechanism in a stationary environment, and where an inflationary monetary mechanism is preferred ex ante to a laissez‐faire or deflationary monetary mechanism in an environment with impatient agents.     

An optimal auction with correlated values and risk aversion

We consider an auction setting where the buyers are risk averse with correlated private valuations (CARA preferences, binary types), and characterize the optimal mechanism for a risk-neutral seller. We show that the optimal auction extracts all buyer surplus whenever the correlation is sufficiently strong (greater than 1/3 in absolute value), no matter how risk averse the buyers are. In contrast, we note that a sufficiently risk-averse seller would not use a full rent extracting mechanism for any positive correlation of the valuations even if the buyers were risk neutral.     

On Nash-Implementation in the Presence of Withholding

In this paper we construct a completely feasible and continuous mechanism whose Nash allocations coincide with Lindahl allocations when both preferences and initial endowments are unknown to the designer and unreported endowments are withheld. This mechanism extends the mechanism of Hong by allowing for semi-positivity of endowments for private goods economies and the mechanism of Tian by allowing for any number of private goods for public goods economies. Thus our mechanism improves all the existing mechanisms that implement Walrasian or Lindahl allocations. Journal of Economic Literature Classification Numbers: C72, D6l, D78, H41.     

Characterizing Natural Implementability: The Fair and Walrasian Correspondences

We characterize natural implementability in exchange economies when a social choice correspondence possibly recommends a Pareto efficient allocation where the common marginal rate of substitution is not determined uniquely. We find that the no-envy and efficient (or fair) correspondence cannot be implemented by any natural mechanism with a price and a quantity announcement, but can be implemented by a natural mechanism with a price and two-quantity announcement. On the other hand, the constrained Walrasian correspondence can be implemented by a natural price-quantity mechanism with budget balance. Journal of Economic Literature Classification Numbers: C72, D51, D63, D78.     

Moral Hazard and Private Monitoring

We clarify the role of mixed strategies and public randomization (sunspots) in sustaining near-efficient outcomes in repeated games with private monitoring. We study a finitely repeated game, where the stage game has multiple equilibria and show that mixed strategies can support partial cooperation, but cannot approximate full cooperation even if monitoring is “almost perfect.” Efficiency requires extensive form correlation, where strategies can condition upon a sunspot at the end of each period. For any finite number of repetitions, we approximate the best equilibrium payoff under perfect monitoring, assuming that monitoring is sufficiently accurate and sunspots are available. Journal of Economic Literature Classification Numbers: C73, D82.     

A Characterization for Dominant Strategy Implementation

We introduce a perfect price discriminating mechanism for allocation problems with private information. A perfect price discriminating mechanism treats a seller, for example, as a perfect price discriminating monopolist who faces a price schedule that does not depend on her report. In any perfect price discriminating mechanism, every player has a dominant strategy to truthfully report her private information.We establish a characterization for dominant strategy implementation: Any outcome that can be dominant strategy implemented can also be dominant strategy implemented using a perfect price discriminating mechanism. We apply this characterization to derive the optimal, budget-balanced, dominant strategy mechanisms for public good provision and bilateral bargaining.     

Social Insurance and Redistribution with Moral Hazard and Adverse Selection*

Rochet (1991) showed that with distortionary income taxes, social insurance is a desirable redistributive device when risk and ability are negatively correlated. This finding is re‐examined when ex post moral hazard and adverse selection are included, and under different informational assumptions. Individuals can take actions influencing the size of the loss in the event of accident (or ill health). Social insurance can be supplemented by private insurance, but private insurance markets are affected by both adverse selection and moral hazard. We study how equity and efficiency considerations should be traded off in choosing the optimal coverage of social insurance when those features are introduced. The case for social insurance is strongest when the government is well informed about household productivity.     

Long‐term care policy with lazy rotten kids

This paper studies the determination of informal long‐term care (LTC) provided by children in a scenario which is somewhere in between perfect altruism and selfish exchanges. Parents are altruistic but children are purely selfish, and neither side can make credible commitments. The model is based on Becker's “rotten kid” specification except that it explicitly accounts for the sequence of decisions. In Becker's world, with a single good efficiency is achieved. We show that when family aid is introduced the outcome is likely to be inefficient. Still, the rotten kid mechanism is at work and ensures that a positive level of LTC is provided as long as the bequest motive is operative. We identify the inefficiencies by comparing the laissez‐faire (subgame perfect) equilibrium to the first‐best allocation. We first assume that families are identical ex ante and then consider the case where dynasties differ in wealth. We study how the provision of LTC can be improved by public policies. Interestingly, crowding out of private aid by public LTC is not a problem in this setting. With an operative bequest motive, public LTC will have no impact on private aid. More amazingly still, when the bequest motive is (initially) not operative, public insurance may even enhance the provision of informal aid.     

Private money and bank runs

Abstract This paper studies bank runs in a model with private money. We show that allowing claims on demand deposits to circulate as a medium of exchange can help prevent bank runs. In our model, there exists a unique banking equilibrium where no one demands early withdrawals of real goods and agents in need of liquidity use private money to finance consumption. With private money, the unique equilibrium not only eliminates bank runs but also improves banking efficiency. The implications of our model are consistent with the evidence from the banking history of the United States.     

The Differential Impact of Public and Private Governance Institutions on the Different Modes of Foreign Investment

This paper examines the respective impacts of public and private governance institutions on foreign direct and foreign portfolio investment inflows. We present two hypotheses: (1) there is a strong correlation between the quality of a country’s public governance institutions and the amount of foreign direct investment (FDI) received while the quality of its private governance institutions has no further discernible impact on this correlation; (2) there is a strong correlation between the quality of a country’s public governance institutions and the amount of foreign portfolio investment (FPI) received while the quality of its private governance institutions has a further positive impact on this correlation. Our findings, which are based on panel data analysis, show both hypotheses to be valid.     

Influence and inefficiency in the internal capital market

I model inefficient resource allocations in M-form organizations due to influence activities by division managers that skew capital budgets in their favor. Corporate headquarters receives two types of signals about investment opportunities: private signals that can be distorted by managers, and public signals that are undistorted but noisy. Headquarters faces a tradeoff between the cost of attaining an accurate private signal and the value of the information the signal provides. In contrast to existing models of “socialism” in internal capital markets, I show that investment sensitivity to Tobin's Q is higher than first-best in firms where division managers hold equity (a result consistent with evidence presented in Scharfstein, 1998). When managers face high private costs from distorting information (equity holdings), headquarters may commit to investment contracts that place “too little” weight on private signals and “too much” weight on public signals (i.e. Q). This result has implications for managers in the design of capital budgeting processes and incentive compensation systems.     

Strategic Complementarity in the Dynamic Private Provision of a Discrete Public Good

Individual voluntary contributions to a discrete public good are shown to be strategic complements in a dynamic private provision game. This is in contrast to a public good that can take on any value in a continuum where they are strategic substitutes.     

The economics of crowd out under mixed public/private health insurance

It is well known that public insurance sometimes crowds out private insurance. Yet, the economic theory of crowd out has remained unstudied. Here, I show that crowd out causes two countervailing effects: (a) the intensive margin effect-since high demanders are crowded out, the private market now has a larger proportion of low demanders on the intensive margin (The intensive margin are those who have already bought private insurance), and so will drop quality to lower the price to the low demanders liking; and (b) the extensive margin effect-before the public insurance expansion, the private sector had lowered quality to make insurance more affordable at the extensive margin (The extensive margin is the next group of people who would buy private insurance if the price decreased), but now that public insurance crowds out the extensive margin, quality can then be raised back up to the high demanders liking.If the extensive margin effect dominates, then a new phenomenon of push out occurs, in which crowd out causes the private sector to raise quality and to increase the number of uninsured low demanders not eligible for public insurance. If the intensive margin effect dominates, then crowd out will cause the private sector to lower quality, causing the phenomenon of crowd-in, in which the number of uninsured low demanders that take-up private insurance increases.These two countervailing effects have important implications for any government policy that desires to eradicate all uninsurance. First, if push out is dominant, then the private sector will respond to the public insurance by pushing out and leaving some people newly uninsured. If crowd-in is dominant, then all people can be insured and the government can do it at a lower-than-anticipated level of expansion due to the private sector crowding in.Received: April 2002, Accepted: February 2003, JEL Classification: I11, I38The views herein do not necessarily reflect the views or policies of AHRQ, nor the U.S. Department of Health and Human Services. I thank Pedro Pita Barros, Hugh Gravelle, and Lise Rochaix-Ranson, and participants at the 2nd Health Economics Workshop at the Universidade Nova de Lisboa for helpful comments.     

Private takings

This paper examines the implications associated with a recent Supreme Court ruling, Kelo v. City of New London (2005). Kelo can be interpreted as supporting eminent domain as a means of transferring property rights from one set of private agents—landowners—to another private agent—a developer. Under voluntary exchange, where the developer sequentially acquires property rights from landowners via bargaining, a holdout problem arises. Eminent domain gives all of the bargaining power to the developer and, as a result, eliminates the holdout problem. This is the benefit of Kelo. However, landowners lose all their bargaining power and, as a result, their property investments become more inefficient. This is the cost of Kelo. A policy of eminent domain increases social welfare compared to voluntary sequential exchange only when the holdout problem is severe, and this occurs only if the developer has very little bargaining power. We propose an alternative government policy that eliminates the holdout problem but does not affect the bargaining power of the various parties. This alternative policy strictly dominates a policy of eminent domain, which implies that eminent domain is an inefficient way to transfer property rights between private agents.     

Dynamic stability and reform of political institutions

This paper examines endogenous institutional change in a class of dynamic political games. The political aggregation rules used at date t+1 are instrumental choices under rules at date t. Effectively, rules are “players” who can strategically delegate future policy-making authority to different rules. A political rule is stable if it selects itself. A reform occurs when an alternative rule is selected. The stability of a political rule is shown to depend on whether its choices are dynamically consistent. For instance, simple majority rules can be shown to be dynamically consistent in many common environments where wealth-weighted voting rules are not. The result extends to political rules that incorporate private activities such as extra-legal protests, threats, or private investment. The approach is one way of understanding various explanations of institutional change proposed in the literature. A parametric model of public goods provision gives an illustration.     

Computationally restricted unmediated talk under incomplete information

Summary. We show the role of unmediated talk with computational complexity bounds as both an information transmission and a coordination device for the class of two-player games with incomplete information and rational parameters. We prove that any communication equilibrium payoff of such games can be reached as a Bayesian-Nash equilibrium payoff of the game extended by a two phase universal mechanism of interim computationally restricted pre-play communication. The communication protocols are designed with the help of modern cryptographic tools. A familiar context in which our results could be applied is bilateral trading with incomplete information.Received: 9 September 2002, Revised: 14 March 2003, JEL Classification Numbers: C72. Correspondence to: Amparo UrbanoWe wish to thank financial aid from the Valencian Institute of Economic Research (IVIE) and partial support by DIGCYT under project PB95 - 1074. A previous version of this work appears as IVIE Working Paper WP-AD 99-07, under the title: "Unmediated talk under incomplete information".     

A Note on the Theory of Charitable Fund-raising: The Role of Refunds

Andreoni (1998, Journal of Political Economy 106 , 1186–1213) shows that a small amount of seed money from the government can generate substantial additional private donations toward the provision of a public good, when there is a threshold level of provision below which no benefits are achieved. We argue that Andreoni's solution can be extended to a mechanism where refunds are possible. We then argue that a greater "bang per buck" may be achieved if the seed money is targeted to cover the administrative costs of providing refunds.