Reputation for quality and adverse selection

We analyze a dynamic market with a seller who can make a one-time investment that affects the returns of tradable assets. The potential buyers of the assets cannot observe the seller׳s investment prior to the trade or verify it in any way after the trade. The market faces two types of inefficiency: the ex-ante inefficiency, i.e., the seller׳s moral hazard problem, and the ex-post inefficiency, i.e., inefficient ex-post allocations due to the adverse selection problem. We analyze how the observability of information by future buyers, through which the seller builds a reputation, affects the two types of inefficiency as well as the interplay between them.     

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.     

Mutual Insurance,Individual Savings,and Limited Commitment

We examine a dynamic model of mutual insurance when households can also engage in self-insurance by storage. We assume that there is no enforcement mechanism, so that any insurance is informal and must be self-enforcing. We show that consumption allocations satisfy a modified Euler condition and that an enhanced storage technology can either improve or diminish welfare. Furthermore we show that the ex ante transfers introduced into dynamic informal insurance models recently by Gauthier et al. (Gauthier, C., Poitevin, M., and González, P. (1997). Journal of Economic Theory76, 106–144) are only used here in the first period, with the role of ex ante transfers being replaced by differential individual storage. Journal of Economic Literature Classification Numbers: C61, C73, D90, E21.     

Voting on Unemployment Insurance

In this article, we ask heterogeneous agents in a dynamic general equilibrium economy to vote on the generosity of their unemployment insurance program. We observe the influence on their vote of (1) moral hazard, (2) private alternatives, and (3) changes in employment status. Agents differ in skills, employment probabilities, income prospects, and assets. For a calibration to the United States, we show that: (1) in contrast to the literature, plausible levels of moral hazard need not induce large cuts in optimal benefits. (2) Switching to private insurance is rejected for most status quo, though it would be as generous. (3) Skill groups vote as a block. For reasonable discount factors, solidarity is never broken simultaneously for more than one group.     

供应商管理库存中的道德风险分析与契约设计

分析了供应商管理库存环境下,除双重边际效应以外另一个导致供应链分散决策时零售商订购量下降的因素,即道德风险问题。针对道德风险,采用求解完全且完美信息动态博弈中子博弈完美纳什均衡的一般方法,即逆推归纳法设计了一个数量折扣契约。当参数满足一定关系时,该契约不仅可以有效消除供应商管理库存中的道德风险,而且也使供销双方期望利润实现了帕累托改进,因此该契约不仅是有效的,而且也是可执行的。     

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.     

Reclaim-proof allocation of indivisible objects

We study desirability axioms imposed on allocations in indivisible object allocation problems. The existing axioms in the literature are various conditions of robustness to blocking coalitions with respect to agentsʼ ex ante (individual rationality and group rationality) and ex post (Pareto efficiency) endowments. We introduce a stringent axiom that encompasses and strengthens the existing ones. An allocation is reclaim-proof if it is robust to blocking coalitions with respect to any conceivable interim endowments of agents. This is an appealing property in dynamic settings, where the assignments prescribed by an allocation to be implemented need to be made in multiple rounds rather than all in one shot. We show that an allocation is reclaim-proof if and only if it is induced by a YRMH–IGYT mechanism (introduced by Abdulkadiroğlu and Sönmez, 1999) and if and only if it is a competitive allocation.     

Efficient allocations with moral hazard and hidden borrowing and lending: A recursive formulation

We propose a tractable recursive framework to study the optimal allocation of consumption and effort in a dynamic setting with moral hazard where agents have secret access to the credit market or to storage. The recursive structure is based on a generalized first-order approach, whose validity must be verified ex post. Thanks to the recursive formulation of the optimal contract, the verification procedure turns out to be numerically parsimonious as it can be performed using standard dynamic programming techniques with only one endogenous state variable: The agent's level of assets. We study the performance of our ex post verification test in practice by solving numerically three representative infinite horizon examples.     

Discounting Nordhaus

This paper evaluates Nordhaus's neoclassical complaints about the Stern Review from the vantage point of classical growth theory. Nordhaus criticizes the Stern Review because it uses a discount rate that is well below the market rate of return on capital. From the perspective of classical growth theory, Nordhaus's belief in choosing preference parameters for the social planner based on observed market rates of return is equivalent to assigning the preferences of the capitalist agents to the social planner. This equivalence is an implication of the Cambridge Theorem, which interprets the Ramsey equation as the saving function of the capitalist agents.     

Coalitional fairness in interim differential information economies

In this paper we propose a concept of coalitional fair allocation in order to solve the tension that may exist between efficiency and envy-freeness when agents are asymmetrically informed and the equity of allocations is evaluated at the interim stage.     

Non-myopic learning in differential information economies: the core

Summary. We study the process of learning in a differential information economy, with a continuum of states of nature that follow a Markov process. The economy extends over an infinite number of periods and we assume that the agents behave non-myopically, i.e., they discount the future. We adopt a new equilibrium concept, the non-myopic core. A realized agreement in each period generates information that changes the underlying structure in the economy. The results we obtain serve as an extension to the results in Koutsougeras and Yannelis (1999) in a setting where agents behave non-myopically. In particular, we examine the following two questions: 1) If we have a sequence of allocations that are in an approximate non-myopic core (we allow for bounded rationality), is it possible to find a subsequence that converges to a non-myopic core allocation in a limit full information economy? 2) Given a non-myopic core allocation in a limit full information economy can we find a sequence of approximate non-myopic core allocations that converges to that allocation? Received: May 25, 1999; revised version: August 9, 1999     

Fixed-term employment contracts in an equilibrium search model

We develop a theoretical model of firm dynamics and unemployment and characterize equilibria with tenure dependent separation taxes. The model is a version of the Lucas and Prescott island model with undirected search. Two equivalent decentralizations are considered: one with spot labor markets and one with long-term employment relations. We model “temporary contracts” as the special case of a separation tax that only applies to workers with tenure higher than J. While in principle these contracts require a J-dimensional state space, equilibrium allocations solve a simple dynamic programming problem characterized by two-dimensional inaction set(s).     

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.     

Existence and fairness of value allocation without convex preferences

Shafer (Econometrica, 48 (1980), 467–476) proved that in a finite exchange economy value allocations exist, provided that each agent has convex, complete, transitive, compact and monotone preferences. However, if preferences are not convex, then value allocations may not exist. To remedy this difficulty we enlarge the set of value allocations by introducing the concept of approximate value allocations, and show that in a finite exchange economy approximate value allocations exist, even if preferences are not convex, or compact, or monotone. This value existence result can be used to provide a very general value existence theorem for a sequence of finite economies. Further, we show that value allocations may discriminate in favor of or against a coalition of agents.     

Recursive preferences and balanced growth

We study a class of utility functions that are defined recursively by an aggregator W(x,y) where u_t=W(c_t,u_t+1). In single-agent economies it is known that a sufficient condition for the existence of a balanced growth path is that utility should be homogenous of degree γ. In the context of a multi-agent economy we show that this restriction implies that either a balanced growth equilibrium fails to exist or all agents have the same constant discount factor. We suggest a generalization of recursive preferences wherein the intertemporal utility function is time dependent. Within this class we establish that there may exist a balanced growth equilibrium even if agents are different.     

Sharing Rules in Teams

We examine the problem of output sharing in a moral hazard in team situation. Although we do not consider any particular procedure, we assume that the team uses some procedure to decide a sharing rule before actual production takes place (for example, this may be a bargaining process or a team welfare maximization problem). This must take into account that the team will play a noncooperative game in the production process conditional on the chosen sharing rule. We show that the procedure for deciding the sharing rule does not have to look for anything more complicated than simple linear sharing rules. We also show that, when there is limited liability, the procedure needs to consider only the slightly more complicated piecewise linear rules. As a consequence of the linear sharing rule result, we are also able to provide a characterization of implementable outcomes. Journal of Economic Literature Classification Numbers: D82, D2, C72, J54.     

Optimal personal bankruptcy design under moral hazard

In this paper, we develop a normative theory of unsecured consumer credit and personal bankruptcy based on the optimal trade-off between incentives and insurance. First, in order to characterize this trade-off, we solve a dynamic moral hazard problem in which agents' private effort decisions influence the life-cycle profiles of their earnings. We then show how the optimal allocation of individual effort and consumption can be implemented in a market equilibrium in which (i) agents and intermediaries repeatedly trade secured and unsecured debt instruments, and (ii) agents obtain (restricted) discharge of their unsecured debts in bankruptcy. The structure of this equilibrium and the associated restrictions on debt discharge closely match the main qualitative features of personal credit markets and bankruptcy law that actually exist in the United States.     

A Theory of Liquidity and Regulation of Financial Intermediation

This paper studies a Diamond–Dybvig model of providing insurance against unobservable liquidity shocks in the presence of unobservable trades. We show that competitive equilibria are inefficient. A social planner finds it beneficial to introduce a wedge between the interest rate implicit in optimal allocations and the economy's marginal rate of transformation. This improves risk sharing by reducing the attractiveness of joint deviations where agents simultaneously misrepresent their type and engage in trades on private markets. We propose a simple implementation of the optimum that imposes a constraint on the portfolio share that financial intermediaries invest in short-term assets.     

Power fluctuations and political economy

We study (constrained) Pareto efficient allocations in a dynamic production economy where the group that holds political power decides the allocation of resources. For high discount factors, the economy converges to a first-best allocation where labor supply decisions are not distorted. For low discount factors, distortions do not disappear and fluctuate over time. Most importantly, the set of sustainable first-best allocations is larger when there is less persistence in the identity of the party in power (because this encourages political compromise). This result contradicts the common presumption that there will be fewer distortions when there is a “stable ruling group”.     

Can Health Savings Accounts Reduce Health Spending? Evidence from China

Health care costs are high and continue to rise in most major economies, and the health savings account (HSA) is often viewed as an appealing way to contain health care costs because it can potentially solve the moral hazard spending caused by traditional health insurance. This study uses data from the China Household Finance Survey (CHFS) to empirically examine the effectiveness of HSAs in containing medical expenses and reducing moral hazard. The findings show that HSAs that restrict the use of funds may lead enrollees to discount the value and thus spend more on health care. In addition, the positive effect of HSAs on medical expenses is larger for the relatively healthier group, which may suggest that moral hazard exists regarding the use of HSA funds. The empirical estimates of the HSA effect on medical expenses are robust when a set of covariates are controlled, and HSA balances are instrumented using housing savings account balances.