General equilibrium in economies with adverse selection

We model economies of adverse selection as Arrow–Debreu economies. In the spirit of Prescott and Townsend (Econometrica 52(1), 21–45, 1984a), we identify the consumption set of the individuals with the set of lotteries over net transfers. Thus, prices are linear in lotteries, but they may be non linear in commodity bundles. First, we study a weak equilibrium notion by viewing the economy of adverse selection as a pure exchange economy. The weak equilibrium set is non empty, but some of the allocations may be inefficient, and the equilibria indeterminate. Second, following Prescott and Townsend (Econometrica 52(1), 21–45, 1984a), we introduce an intermediary (firm) supplying feasible and incentive compatible measures. Equilibria are constrained efficient, but the equilibrium set is empty for an open set of economies containing the Rothschild and Stiglitz insurance economies. The research of A. Rustichini was supported by the NSF grant NSF/SES-0136556.     

Direct versus intermediated finance: An old question and a new answer

We consider a closed economy where a risk neutral bank competes with a competitive bond market. Firms can finance a risky project either by a bank credit or by issuing a bond which is directly sold to risk averse investors who also hold safe deposits at the bank. We show that the bank tends to allocate more capital to lower quality projects but there are some interesting qualifications. If the asymmetric information concerns only the success probability, then we observe adverse selection while if it concerns only the expected return, bad types are driven out of the market.     

银行资产证券化的风险自留监管：作用机制和福利效果

本文首先建立了一个两期模型的理论框架,分析当银行将信息不透明的资产通过证券化卖给连续统个市场投资者时,风险自留监管的效果。基本模型的分析发现:首先,单一风险自留比例不具有普适性;最优风险自留比例与基础资产的风险收益特征、交易双方的风险态度都密切相关。其次,风险自留监管会降低差资产证券化数量的有效信息含量,从而加剧逆向选择程度;而对于好资产,又存在发信号成本。本文进而从道德风险的角度证明,银行的风险态度会影响单一风险自留要求是否能够提高银行监督贷款的激励。因此,在实施风险自留监管时,政府应当结合银行和投资者的风险规避程度等具体情况有针对性地进行,从而比单一风险自留监管更好地提高社会福利。     

Conformism,peer pressure and adverse selection

To examine the effects of peer pressure in adverse selection problem, we define a peer pressure function that represents the psychological costs and incorporate it into the agent's utility function. Based on these assumptions, the efficient agent who has conformity preference produces less outputs than the first-best level, while the inefficient agent produces more than the second-best level of standard adverse selection output when the agents feel peer pressure among themselves. Although the production gap between the utility functions under peer pressure narrows, the gap of the ex post information rent goes wider as the information rent of efficient agents increases. Our theoretical results are consistent with some empirical/experimental findings.     

Genetic adverse selection: Evidence from long-term care insurance and Huntington disease

Individual, personalized genetic information is increasingly available, leading to the possibility of greater adverse selection over time, particularly in individual-payer insurance markets. We use data on individuals at risk for Huntington disease (HD), a degenerative neurological disorder with significant effects on morbidity, to estimate adverse selection in long-term care insurance. We find strong evidence of adverse selection: individuals who carry the HD genetic mutation are up to 5 times as likely as the general population to own long-term care insurance. This finding is supported both by comparing individuals at risk for HD to those in the general population and by comparing across tested individuals in the HD-risk population with and without the HD mutation.     

Signaling in markets with two-sided adverse selection

Summary. The paper analyzes an economy with two-sided adverse selection, focusing on equilibria that satisfy a refinement based on the notion of strategic stability. In the familiar case of one-sided adverse selection, agents reveal all of their private information as long as the contract space is rich enough. However, with two-sided adverse selection, the sufficient conditions for separation are much stronger. Received: September 3, 1999; revised version: December 3, 1999     

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.     

State-uncertainty preferences and the risk premium in the exchange rate market

This paper shows that state-uncertainty preferences help to explain the observed exchange rate risk premium. In the framework of Lucas (1982) economy, state-uncertainty preferences amount to assuming that a given level of consumption will yield a higher level of utility the lower is the level of uncertainty perceived by consumers. Under these preferences we can distinguish between two factors driving the exchange rate risk premium: “macroeconomic risk” and “the risk associated with variation in the private agents' perception on the level of uncertainty”. Empirical evidence from three main European economies in the transition period to the euro provides empirical support for the model. The model is more successful in accounting for the observed currency risk premium than models with more standard preferences, and the general perception of risk by private agents is shown to be a more important determinant of risk premium than macroeconomic uncertainty.     

Community rating and the market for private non-group health insurance

Prior research on adverse selection in health insurance markets has found only mixed evidence for adverse selection in group settings. We examine the impact of state community rating regulations enacted in the 1990s, which greatly limited insurers' ability to risk rate premiums, to determine if adverse selection is more evident in non-group insurance markets. Using data from large, national surveys we find evidence of a shift to a less healthy pool of non-group enrollees as a consequence of community rating. Community rating made healthy people 20 to 60% less likely to be insured by non-group health insurance; in addition, we found evidence that young and healthy people were 20 to 30% more likely to be uninsured as a result of community rating. We also find evidence that individuals in poor health were 35 to 50% more likely to be insured in the non-group market, but only limited evidence suggesting that persons in poor health were less likely to be uninsured. Our results are further supported by findings suggesting that non-group enrollees were sicker as a result of the community rating laws. Lastly, we find evidence suggesting that HMO penetration in the non-group market increased disproportionately in states that implemented community rating relative to states that did not.     

Decreasing absolute prudence: Characterization and applications to second-best risk sharing

In this paper, we provide two basic properties of utility functions u which exhibit decreasing absolute prudence i.e. (− u/u″)′ ≤ 0. These properties are used to examine the allocation of risks in an economy when some agents bear non-transferable risks. We show that it is fair Pareto-efficient to let those with a non-transferable risk bear relatively less of the transferable risk in the economy if and only if absolute prudence is decreasing. In another model, there is a complete set of contingent markets, but some agents have no direct access to them. We examine the fair efficient allocation of risk in a pool gathering a trader and a non-trader. Decreasing absolute prudence provides an upper bound to the share of the pool's risk that should be borne by the trader.     

Complementarity and Substituability in Multiple-Risk Insurance Markets

We study imperfect competition between insurers in a multiple-risk environment. In the absence of asymmetric information, equilibria are efficient, and we determine the degrees of specialization under which the specialized insurers are able or unable to capture the surplus. We show in contrast that under adverse selection, specialization systematically prevents second-best efficiency. Concluding on the role of our notions of strategic complementarity/substituability on the tradeoff between efficiency and fairness of the allocation, we give indications on the desirable structure of the insurance industry.     

Insurance contracts with imprecise probabilities and adverse selection

Summary. This article deals with optimal insurance contracts in the framework of imprecise probabilities and adverse selection. Agents differ not only in the objective risk they face but also in the perception of risk. In monopoly, a range of configurations that VNM preferences preclude appears: a pooling contract may be optimal, incomplete coverage may be offered to high risks, low risks may be better covered.Received: 1 November 2001, Revised: 15 April 2003, JEL Classification Numbers: D81, D82, G22.Useful suggestions by Emmanuelle Auriol, Bernard Bensaïd, Michéle Cohen, Isaac Meilijson and the anonymous referee are acknowledged. Correspondence to: M. Jeleva     

To Trade Or Not To Trade: Economies With A Variable Number Of Tradeables*

We present a general equilibrium model that encompasses the endogenous selection and shadow‐pricing of a set of tradeable commodities, with home‐based and social production activities. In the model, a market system is a set of costly social institutions which embody the trade and production technologies available in the economy. Our equilibrium concept describes the pricing of market institutions, thus pricing the tradeability of a commodity. We obtain the existence and the decentralization of Pareto‐efficient allocations. We discuss an example regarding the transition of a guild‐based economy into a market‐based economy.     

Partnerships, lemons, and efficient trade

We analyze the possibility of efficient trade with informationally interdependent valuations and with a dispersed ownership. A main role is played by the effects of adverse selection on incentive payments and budget constraints. Variations in the degree of interdependence directly influence the incentive payments and ultimately lead to a tightening or relaxation of the budget constraint, thus affecting the ability to achieve efficient trade. We derive precise possibility conditions for efficient trade, and we offer a framework in which the interplay of insights previously obtained by Akerlof (Quart. J. Econom. 89 (1970) 488), Myerson and Satterthwaite (J. Econom. Theory 28 (1983) 265), and Cramton et al. (Econometrica 55 (1987) 615) can be analyzed. In addition, we discuss to what extent possibility results previously obtained for private values environments can be generalized.     

Representative consumer's risk aversion and efficient risk-sharing rules

We study the representative consumer's risk attitude and efficient risk-sharing rules in a single-period, single-good economy in which consumers have homogeneous probabilistic beliefs but heterogeneous risk attitudes. We prove that if all consumers have convex absolute risk tolerance, so must the representative consumer. We also identify a relationship between the curvature of an individual consumer's individual risk sharing rule and his absolute cautiousness, the first derivative of absolute risk-tolerance. Furthermore, we discuss some consequences of these results and refinements of these results for the class of HARA utility functions.     

Optimal contract mechanisms for principal-agent problems with moral hazard and adverse selection

Summary We examine the problem of incentive compatibility and mechanism design for incomplete information principal-agent problems. Allowing for risk aversion on the part of the principal and agent, we show the existence of an optimal, incentive compatible contract selection mechanism for the principal under conditions of moral hazard and adverse selection. Since we assume that the contract set is a function space of state contingent contracts, and that the set of agent types is uncountable, the set of contract selection mechanisms becomes infinite dimensional. Hence, novel existence arguments are required. Our existence result extends those of Grossman and Hart [10] and Page [23] to an infinite dimensional setting with incomplete information.     

Social security and risk sharing

In this paper we identify conditions under which the introduction of a pay-as-you-go social security system is ex ante Pareto-improving in a stochastic OLG economy with capital accumulation and land. We argue that these conditions are consistent with realistic specifications of the parameters of the economy. In our model financial markets are complete and competitive equilibria interim Pareto efficient. Therefore, a welfare improvement can only be obtained if agents? welfare is evaluated ex ante, and arises from an improvement in intergenerational risk sharing. We also examine the optimal size of a given social security system as well as its optimal reform.     

从经济学角度看“经济适用房货币补贴政策”的弊端

从经济学角度来看,经济适用房货币补贴政策不但会对普通住宅市场产生冲击,而且对单个家庭效用也不具有可持续性,同时还避免不了逆向选择和道德风险的问题。因此,经济适用房货币补贴政策的推行,利少弊多,应当＂慎用＂。     

Limit order books,uninformed traders and commodity derivatives: Insights from the European carbon futures

This paper provides a suitable model for studying the strategic behavior of uninformed investors that trade commodity derivatives via limit order books. Two main testable implications are obtained after solving for the model equilibrium. The adverse selection costs of uninformed traders depend on the inflow of market orders and their risk aversion. Next, the adverse selection costs of uninformed buyers and sellers and the difference of their asset valuations determine the size of their bid-ask spread.An analysis of European carbon futures data confirms the relevance of these implications. Moreover, we detect a diagonal effect that results in a positive correlation of market orders, which is driven by adverse selection, then by order splitting strategies and by imitative strategies of uninformed traders to a lesser extent.