Negative Externalities and Evolutionary Implementation

We model externality abatement as an implementation problem. A social planner would like to ensure efficient behaviour among a group of agents whose actions are sources of externalities. However, the planner has limited information about the agents' preferences, and is unable to distinguish individual agents except through their action choices. We prove that if a concavity condition on aggregate payoffs is satisfied, the planner can guarantee that efficient behaviour is globally stable under a wide range of behaviour adjustment processes by administering a variable pricing scheme. Through a series of applications, we show that the concavity condition is naturally satisfied in settings involving negative externalities. We conclude by contrasting the performance of the pricing mechanism with that of a mechanism based on direct revelation and announcement dependent forcing contracts.     

Learning Dynamics with Private and Public Signals

This paper studies the dynamics of learning in a model of technology adoption. Firms learn about an unknown technology by observing both private and public signals. Because of the externality associated with the public signal, the social planner has firms experiment more in the initial period of the model, relative to the market equilibrium. In certain cases, this more rapid generation of information results in the planner experimenting less in later periods of the model. In contrast, typical models with public signals result in the planner inducing more experimentation in all periods of the model relative to the market equilibrium. I would like to thank Matt Mitchell and Tom Holmes for their advice and encouragement. I would also like to thank Thor Koeppl, Cyril Monnet, John Stevens, and Jason Cummins, and two anonymous referees for their helpful comments. This paper is the second chapter of my dissertation. The views expressed herein are my own and not necessarily those of the Bureau of Economic Analysis or the US Department of Commerce.     

The Important Thing Is Not (Always) Winning but Taking Part: Funding Public Goods with Contests

This paper considers a public good game with heterogeneous endowments and incomplete information affected by extreme free riding. I overcome this problem through the implementation of a deterministic contest in which several prizes may be awarded. I identify a monotone equilibrium, in which the contribution is strictly increasing in the endowment. I prove that it is optimal for the social planner to set the last prize equal to zero, but otherwise total expected contribution is invariant to the prize structure. Finally, I show that private provision via a contest Pareto‐dominates public provision and is higher than the total contribution raised through a lottery.     

Money and capital as competing media of exchange

We construct a model where capital competes with fiat money as a medium of exchange, and establish conditions on fundamentals under which fiat money can be both valued and socially beneficial. When the socially efficient stock of capital is too low to provide the liquidity agents need, they overaccumulate productive assets to use as media of exchange. When this is the case, there exists a monetary equilibrium that dominates the nonmonetary one in terms of welfare. Under the Friedman Rule, fiat money provides just enough liquidity so that agents choose to accumulate the same capital stock a social planner would.     

Quality Competition and Social Welfare in Markets with Partial Coverage: New Results*

We use a vertical product differentiation model under partial market coverage to study the social welfare optimum and duopoly equilibrium when convex costs of quality provision are either fixed or variable in terms of production. We show the following new results. First, under fixed costs, the social planner charges a uniform price for the single variant that just covers costs of quality provision. Like the duopoly equilibrium, this socially optimal pricing entails a partially uncovered market, but a smaller share of the market is served compared with the duopoly equilibrium. Second, for the variable cost case, it is socially optimal to provide both high‐ and low‐quality variants, but market shares need not be equal. This differs from the result in fully covered markets. Third, in the duopoly equilibrium, the quality spread is too wide under variable costs relative to the social optimum. Under fixed costs, the duopoly produces two variants, but quality is too low relative to the social optimum, which has only one variant.     

Transaction costs and planner intervention

In this paper, I examine a two-period general equilibrium model in which transaction costs are incurred whenever financial contracts are traded. These transaction costs are real and convex. The presence of these transaction costs results in a Pareto inefficient equilibrium allocation. Attempting to fix this problem, the planner will intervene by scaling the transaction costs either up or down. The intervention must satisfy fiscal balance meaning that the summed value of transaction costs will remain constant. I prove that over a generic subset of household utility functions and endowments and subject to an upper bound on the number of household types, there exists an open set of planner interventions that lead to a Pareto superior allocation.     

A Dynamic Analysis of the Market for Wide-Bodied Commercial Aircraft

This paper uses an empirical dynamic oligopoly model of the commercial aircraft industry to analyse industry pricing, industry performance, and optimal industry policy. A novel feature of the model with respect to the previous literature is that entry, exit, prices, and quantities are endogenously determined in Markov perfect equilibrium (MPE). We find that many unusual aspects of the aircraft data, such as high concentration and persistent pricing below static marginal cost, are explained by this model. We also find that the unconstrained MPE is quite efficient from a social perspective, providing only 10% less welfare on average than a social planner would obtain. Finally, we provide simulation evidence that an anti-trust policy in the form of a concentration restriction would be welfare reducing.     

Efficient Sorting in a Dynamic Adverse-Selection Model

We discuss a class of markets for durable goods where efficiency (or approximate efficiency) is obtained despite the presence of information asymmetries. In the model, the number of times a good has changed hands (the vintage of the good) is an accurate signal of its quality, each consumer self-selects into obtaining the vintage that the social planner would have assigned to her, and consumers' equilibrium trading behaviour in secondary markets is not subject to adverse selection. We show that producers have the incentive to choose contracts that lead to the efficient allocation, and to supply the efficient output. We also provide a contrast between leasing contracts, resale contracts, and different kinds of rental contracts. Resale contracts do not lead to the efficient allocation. A specific kind of rental contract provides the appropriate incentives to consumers.     

State-owned enterprises as indirect instruments of entry regulation

In the context of mixed markets, Matsumura and Kanda (J Econ 84(1): 27–48, 2005) show that social welfare in free entry equilibrium is maximized when there exists a public firm in the market. En passant, these authors state that this outcome is connected to the entry-deterring influence of a public firm. In this way, they counter-act the excess entry problem of Mankiw and Whinston (Rand J Econ 17(1): 48–58, 1986). We explain this result arguing that the state-owned firm can be an indirect instrument to regulate entry. In fact, under free entry equilibrium welfare may be greater with the presence of a public firm than with a social planner.      

Nash implementation and uncertain renegotiation

We study Nash implementation when the outcomes of the mechanism can be renegotiated among the agents but the planner does not know the renegotiation function that they will use. We characterize the social objectives that can be implemented in Nash equilibrium when the same mechanism must work for every admissible renegotiation function, and show the importance of allowing the planner to sometimes take away resources from the agents.     

On the equilibrium and welfare consequences of getting ahead of the Smiths

This paper provides an analysis of the social consequences of people seeking to get ahead of the Smiths. All individuals attempt to reach a higher rank than the Smiths, including the Smiths themselves. This attitude gives rise to an equilibrium in which all individuals have equal utilities but unequal (gross) incomes. Due to a rat‐race effect, individuals devote too much energy to climbing the social scale. However, laissez‐faire equilibrium is an equal‐utility constrained social optimum. Conversely, a utilitarian social planner would not choose utility equality. Unexpectedly, this social ambition theory fairly well accounts for empirical intermediate wage inequality.     

SOCIAL NORMS,LOCAL INTERACTION,AND NEIGHBORHOOD PLANNING*

This article examines optimal social linkage when each individual's repeated interaction with each of his neighbors creates spillovers. Each individual's discount factor is randomly determined. A planner chooses a local interaction network or neighborhood design before the discount factors are realized. Each individual then plays a repeated Prisoner's Dilemma game with his neighbors. A local trigger strategy equilibrium (LTSE) describes an equilibrium in which each individual conditions his cooperation on the cooperation of at least one “acceptable” group of neighbors. Our main results demonstrate a basic trade‐off in the design problem between suboptimal punishment and social conflict. Potentially suboptimal punishment arises in designs with local interactions since in this case monitoring is imperfect. Owing to the heterogeneity of discount factors, however, greater social conflict may arise in more connected networks. When individuals' discount factors are known to the planner, the optimal design exhibits a cooperative “core” and an uncooperative “fringe.”“Uncooperative” (impatient) types are connected to cooperative ones who tolerate their free riding so that social conflict is kept to a minimum. By contrast, when the planner knows only the ex ante distribution over individual discount factors, then in some cases the optimal design partitions individuals into maximally connected cliques (e.g., cul‐de‐sacs), whereas in other cases incomplete graphs with small overlap (e.g., grids) are possible.     

A concern about low relative income, and the alignment of utilitarianism with egalitarianism

A utilitarian social planner who maximizes social welfare assigns the available income to those who are most efficient in converting income into utility. However, when individuals are concerned about their income falling behind the incomes of others, the optimal income distribution under utilitarianism is equality of incomes.     

The Optimal Timing of Procurement Decisions and Patent Allocations*

In a patent race, social incentives and private incentives may sometimes coincide and at other times diverge – too many researchers remain in the race. If the social planner cannot determine what stage the researchers have achieved, this informational constraint can result in a socially suboptimal outcome. We construct a mechanism in which a planner exploits the researchers' private information to determine when and to whom to allocate rights to pursue the final prize. This mechanism does not require any payments and, therefore, will not distort earlier investment incentives. It is solvable by the iterative elimination of dominated strategies.     

On Welfare Criteria and Optimality in an Endogenous Growth Model

In this paper, we explore the consequences for optimality of a social planner adopting two different welfare criteria. The framework of analysis is an overlapping generations model with physical and human capital. We first show that, when the social welfare function is a discounted sum of individual utilities defined over consumption per unit of natural labor, the precise cardinalization of the individual utility function becomes crucial for both the characterization of the social optimum and the policies that support it. Also, decentralizing the social optimum requires an education subsidy that is definitely positive, but its size depends in a determinant way on the aforementioned cardinalization. In contrast, when the social welfare function is a discounted sum of individual utilities defined over consumption per unit of efficient labor, the precise cardinalization of preferences becomes irrelevant. More strikingly, along the optimal growth path, the education subsidy is negative, i.e., the planner should tax rather than subsidize investments in human capital.     

Wage bargaining and turnover costs with heterogenous labor and perfect history screening

We study effects of mobility costs in a model of (Nash) wage bargaining between workers and firms, with instantaneous matching, heterogeneous workers, identical firms and free firm entry, and where firms can screen workers perfectly according to their previous work history but not their actual productivity. We derive the employment level and the minimum worker quality standard, in the market solution, and in the efficient solution established by a social planner. When workers have positive bargaining power, there is always some inefficient unemployment among desired workers in the market solution. The lowest hiring standard chosen by firms is higher than the planner's standard when firing costs are high relative to hiring costs, but may be lower in the opposite case. We show that any higher established hiring standard corresponds to a market equilibrium. The model explains a tendency for a high initial unemployment rate to remain high, particularly for low-skilled workers.     

Statistical Discrimination and Efficiency

This paper asks whether statistical discrimination is a market failure. I consider the problem for a utilitarian social planner who operates in an environment that can generate statistical discrimination as an equilibrium phenomenon. It is found that there are potential efficiency gains from discrimination in terms of reduced "mismatch" between workers and jobs. Whether the solution to the planning problem involves discrimination depends on the trade-off between the informational gains of specialization and the losses in terms of increased investment costs.     

Implementation with partial provability

We extend implementation theory by allowing the social choice function to depend on more than just the preferences of the agents and allowing agents to support their statements with hard evidence. We show that a simple condition on evidence is necessary for the implementation of a social choice function f when the preferences of the agents are state independent and sufficient for implementation for any preferences (including state dependent) with at least three agents if the social planner can perform small monetary transfers beyond those called for by f. If transfers can be large, f can be implemented in a game with perfect information when there are at least two players under a boundedness assumption. For both results, transfers only occur out of equilibrium. The use of evidence enables implementation which is robust in the sense that the planner needs little information about agents? preferences or beliefs and agents need little information about each others? preferences. Our results are robust to evidence forgery at any strictly positive cost.     

Implementation,Elimination of Weakly Dominated Strategies and Evolutionary Dynamics

This paper studies convergence and stability properties of T. Sjöström's (1994, Games Econom. Behav.6, 502–511) mechanism, under the assumption that boundedly rational players find their way to equilibrium using monotonic evolutionary dynamics and best-reply dynamics. This mechanism implements most social choice functions in economic environments using as a solution concept one round of deletion of weakly dominated strategies and one round of deletion of strictly dominated strategies. However, there are other sets of Nash equilibria, whose payoffs may be very different from those desired by the social choice function. With monotonic dynamics, all these sets of equilibria contain limit points of the evolutionary dynamics. Furthermore, even if the dynamics converge to the “right” set of equilibria (i.e., the one which contains the solution of the mechanism), it may converge to an equilibrium which is worse in welfare terms. In contrast with this result, any interior solution of the best-reply dynamics converges to the equilibrium whose outcome the planner desires. Journal of Economic Literature Classification Numbers: C72, D70, D78.     

Bayes–Nash equilibria of the generalized second-price auction

We develop a Bayes–Nash analysis of the generalized second-price (GSP) auction, the multi-unit auction used by search engines to sell sponsored advertising positions. Our main result characterizes the efficient Bayes–Nash equilibrium of the GSP and provides a necessary and sufficient condition that guarantees existence of such an equilibrium. With only two positions, this condition requires that the click–through rate of the second position is sufficiently smaller than that of the first. When an efficient equilibrium exists, we provide a necessary and sufficient condition for the auction revenue to decrease as click–through rates increase. Interestingly, under optimal reserve prices, revenue increases with the click–through rates of all positions. Further, we prove that no inefficient equilibrium of the GSP can be symmetric. Our results are in sharp contrast with the previous literature that studied the GSP under complete information.