Pareto optima and equilibria when preferences are incompletely known

An exchange economy in which agents have convex incomplete preferences defined by families of concave utility functions is considered. Sufficient conditions for the set of efficient allocations and equilibria to coincide with the set of efficient allocations and equilibria that result when each agent has a utility in her family are provided. Welfare theorems in an incomplete preferences framework therefore hold under these conditions and efficient allocations and equilibria are characterized by first order conditions.     

Optimal policy with credibility concerns

This paper considers a reputation model of optimal taxation in which the public is unsure about the government type. A long-lived government can be trustworthy (meaning that it commits to its announced tax rate) or opportunistic (meaning that it retains the ability to change its tax rate after announcing it). Unlike in most prior studies, the committed strategy in this model is optimally chosen by the trustworthy type. We show that this change has significant consequences for the equilibrium dynamics. The optimal committed strategy is found to vary with the time preferences of the two government types, the initial reputation of the government, and the elasticity of household production. This formulation explains differences in policy responses across governments in the face of similar credibility problems.     

Stability and limit cycles in one-dimensional dynamic optimisations of competitive agents with a market externality

This paper considers low dimensional (more precisely, one state variable) dynamic optimisation problems of competitive agents. These individual decisions lead to a dynamic externality for the evolution of the system. However, the impact of an individual and competitive agent is negligible and thus each agent considers this evolution as exogenous data. This leads, assuming rational expectations (perfect foresight due to the deterministic set up), to motions in the three dimensional space of state, costate and externality. Considering the fact that such externalities are widespread, e.g., R&D in the literature on new growth theory, pollution in environmental economics, etc., the incorporation of such externalities due to competitive markets is important, yet this incorporation may alter the stability of the system. Indeed, complex policies such as stable limit cycles are sustainable in such a low-dimensional economy, even for a separable and strictly concave model.     

A note on the global stability condition of price adjustment processes on the plane

In Mukherji [Global stability condition on the plane: a general law of demand, J. Econ. Theory 134 (2007) 583-592], a set of sufficient conditions for global stability of price adjustment processes on the plane is identified. The aim of this note is to point out that one of the conditions can be dropped.     

Environmental regulation of technically inefficient firms

This paper presents a model in which a technically inefficient firm is responsible for the emissions of pollutants. We derive second-best regulatory schemes (tax and quota) assuming that the firm’s technical efficiency is unknown to the regulator.     

Non-marketed options, non-existence of equilibria, and non-linear prices

This paper presents a surprising example that shows that the lattice theoretic properties in Mas-Colell's (1986) seminal work are relevant to the existence of equilibrium even when the commodity space is finite dimensional.The example is a two-period securities model with a three-dimensional portfolio space and two traders. The paper identifies a non-marketed call option that fails to have a minimum cost super-replicating portfolio. Using this option, we construct an economy that satisfies all of Mas-Colell's assumptions, except that the three-dimensional commodity space is not a vector lattice. In this economy, there is no Walrasian equilibrium and the second theorem of welfare economics fails.Our example has important finite- as well as infinite-dimensional implications. It is also an example of a “well behaved” economy in which optimal allocations that are not supported by linear Walrasian prices are decentralized by the non-linear prices studied in Aliprantis-Tourky-Yannelis (2001).     

Linear and non-linear price decentralization

Compendious and thorough solutions to the existence of a linear price equilibrium problem, the second welfare theorem, and the limit theorem on the core are provided for exchange economies whose consumption sets are the positive cone of arbitrary ordered Fréchet spaces—dispensing entirely with the assumption that the vector ordering of the commodity space is a lattice. The motivation comes from economic applications showing the need to bring within the scope of equilibrium theory vector orderings that are not lattices, which arise in the typical model of portfolio trading with missing options. The assumptions are on the primitives of the model. They are bounds on the marginals of non-linear prices and for ω-proper economies they are both sufficient and necessary.     

Decentralization of Pareto optima in economies with public projects,nonessential private goods and convex costs

Summary In the theory of economies with public goods one usually considers the case in which private goods are essential, i.e., each agent receives a fixed minimum level of utility if he consumes no private goods, irrespective of the public goods consumed. This paper develops the second welfare theorem for economies with public projects and possibly inessential private goods. As a corollary we also derive conditions under which valuation equilibria exist.hank Dolf Talman and an anonymous referee for many useful remarks and annotations of a previous draft of this paper.     

Markets with infinitely many commodities and a continuum of agents with non-convex preferences

Summary Contrary to the finite dimensional set-up, the hypothesis of an atomless measure space of traders does not entail convexity of aggregate demand sets if there are infinitely many commodities. In this paper an assumption is introduced which sharpens the non-atomicity hypothesis by requiring that there are many agents of every type. When this condition holds, aggregate demand in an infinite dimensional setting becomes convex even if individual preferences are non-convex. This result is applied to prove the existence of competitive equilibria in such a context.Thanks to E. Dierker, K. Milford, M. Nermuth, C. Puppe, and N. Yannelis for comments and suggestions.     

Dynamic contracting with persistent shocks

In this paper, we develop continuous-time methods for solving dynamic principal-agent problems in which the agent's privately observed productivity shocks are persistent over time. We characterize the optimal contract as the solution to a system of ordinary differential equations and show that, under this contract, the agent's utility converges to its lower bound—immiserization occurs. Unlike under risk-neutrality, the wedge between the marginal rate of transformation and a low-productivity agent's marginal rate of substitution between consumption and leisure will not vanish permanently at her first high-productivity report; also, the wedge increases with the duration of a low-productivity report. We apply the methods to numerically solve the Mirrleesian dynamic taxation model, and find that the wedge is significantly larger than that in the independently and identically distributed (i.i.d.) shock case.     

Efficiency and information aggregation in large uniform-price auctions

We prove that the equilibria of a large interdependent-value, uniform-price auction model where bidders have arbitrary preferences for multiple units can be approximated by a nonatomic exchange economy. We show that the uniform-price auction is approximately efficient with a large number of participants and asymptotically aggregates idiosyncratic bidder information into the market price. More generally our analysis framework provides conditions justifying the use of nonatomic limit model approximations to analyze the large-market behavior of game-theoretic models. We demonstrate continuity requirements on the economic primitives sufficient for the equilibrium strategies of the two models to converge as the number of participants in the finite game approaches infinity.     

An efficient solution to the informed principal problem

In this paper I study mechanism design by an informed principal. I show that generically this problem has an ex-post efficient solution. In the equilibrium mechanism, the informed principal appropriates all expected social surplus, with each type of her getting all expected social surplus conditional on that type. This outcome is supported as a perfect sequential equilibrium of the informed principal game when the joint probability distribution from which the agents’ types are drawn satisfies two conditions: the well-known condition of Cremer and McLean and Identifiability condition introduced by Kosenok and Severinov [Individually rational, budget-balanced mechanisms and allocation of surplus, J. Econ. Theory (2002), forthcoming]. Conversely, these conditions are necessary for an ex-post efficient outcome to be attainable in an equilibrium of the informed principal game. Under these conditions only our equilibrium outcome constitutes a neutral optimum, i.e. cannot be eliminated by any reasonable concept of blocking [R. Myerson, Mechanism design by an informed principal, Econometrica 51 (1983) 1767-1797]. Identifiability and Cremer-McLean conditions are generic when there are at least three agents, and none of them has more types than the number of type profiles of the other agents.     

Externalities and fundamental nonconvexities: A reconciliation of approaches to general equilibrium externality modeling and implications for decentralization

Starrett (1972) [33] and Boyd and Conley (1997) [7] approaches to externality modeling are unified by distinguishing between producible and nonproducible public commodities. Nonconvexities are associated with detrimental producible public commodities but not with nonproducible public commodities in Boyd and Conley (1997) [7]. Disposability properties (costly or costless) imply that producible public commodities are either by-products (e.g., pollution) or joint-products (e.g., national defense). Markets fail for both beneficial and detrimental by-products. Nonconvexities imply that price-based equilibria, e.g., Pigovian tax equilibrium, may not be Pareto-efficient. Foley's (1967, 1970) [17] and [18] “public competitive equilibrium” combines price and quantity signals with a unanimity criterion and restores the equivalence between equilibrium and efficiency.     

Individual protection against property crime: decomposing the effects of protection observability

Abstract.  We re-examine the efficiency of observable and unobservable crime protection decisions with new results and insights. Observable protection is unambiguously associated with a negative externality. At the individual level, it reduces the crime effort, but its unit payoff remains unchanged. Conversely, unobservable protection reduces the unit payoff and has no effect on the crime effort exerted, though it deters crime globally. A decrease in the global crime payoff is detrimental to a victim if protection is observable, while it is beneficial when unobservable. While observable protection has a positive diversion effect, it has the opposite effect when unobservable.     

The benefits of central bank's political independence

We consider a two-tier model of monetary policy where the central banker is both subject to the explicit influence of elected political principals through contracts and the implicit influence of interest groups willing to capture monetary policy. We analyze the impact of granting independence to the central banker on the scope for capture and the agency costs of delegating the monetary policy to a central banker. Political independence increases those agency costs but significantly stabilizes the politically induced fluctuations of inflation and improves ex ante social welfare.     

Optimal taxation with endogenously incomplete debt markets

Empirical analyses of labor tax and public debt processes provide prima facie evidence for imperfect government insurance. This paper considers a model in which the government's inability to commit to future policies or to report truthfully its spending needs renders government debt markets endogenously incomplete. A method for solving for optimal fiscal policy under these constraints is developed. Such policy is found to be intermediate between that implied by the complete insurance (Ramsey) model and a model with exogenously incomplete debt markets. In contrast to optimal Ramsey policy, optimal policy in this model is consistent with a variety of stylized fiscal policy facts such as the high persistence of labor tax rates and debt levels and the positive covariance between government spending and the value of government debt sales.     

Mechanism design with collusive supervision

We analyze an adverse selection environment with third party supervision. The supervisor is partly informed of the agent's type. The supervisor and the agent collude while interacting with the principal. Contracting with the agent directly and ignoring the presence of the supervisor constitutes the no-supervision benchmark. We show that delegating to the supervisor reduces the principal's payoff compared to the no-supervision benchmark under a standard condition on the distribution of the agent's types. In contrast, if the principal contracts with both the agent and the supervisor, there exists a mechanism that improves the principal's payoff over the no-supervision payoff.     

A dual characterization of incentive efficiency

We show that incentive efficient allocations in economies with adverse selection and moral hazard problems can be determined as optimal solutions to a linear programming problem and we use duality theory to obtain a complete characterization of the optima. Our dual analysis identifies welfare effects associated with the incentives of the agents to truthfully reveal their private information. Because these welfare effects may generate non-convexities, incentive efficient allocations may involve randomization. Other properties of incentive efficient allocations are also derived.     

Dynamic inefficiency in an overlapping generations economy with production

Reichlin [Equilibrium cycles in an overlapping generations economy with production, J. Econ. Theory 40 (1986) 89-102] has shown in an OLG model with productive capital that whenever the steady state is locally indeterminate and undergoes a Hopf bifurcation, it is Pareto-optimal. While these results were established under the assumption of Leontief technology, the author has partially extended them to show that the Hopf bifurcation is robust with respect to the introduction of capital-labor substitution. In this note, we prove that the Pareto-optimality of the steady state does not extend to technologies with capital-labor substitution. When the steady state is a sink or undergoes a Hopf bifurcation, it is characterized by over-accumulation with respect to the Golden Rule—the interest rate is negative—hence not Pareto-optimal. Most importantly, it follows that stabilization policies targeting the steady state leave room for welfare losses associated with productive inefficiency, apart from the very special case of Leontief technology.     

Formation of buyer-seller trade networks in a quality-differentiated product market

Abstract .  We examine the formation of buyer-seller links when exchange can take place only if such a link exists. Sellers produce products of different qualities, and multiple sellers can form a sellers' association to pool their customers setting uniform prices. Buyers form trade links with individual sellers or sellers' associations. We show which buyer-seller links will form and find the set of links that are stable and show how these links influence prices. We also show that a trade network mismatch may occur where a high-quality good remains unsold even without an economy-wide excess supply of goods.