Matching markets with adverse selection

This paper considers a market with adverse selection in the spirit of Rothschild and Stiglitz (Quart. J. Econ. 90 (1976) 629). The major departure from existing approaches is that we model a decentralized market that is open-ended and constantly refilled by new participants, e.g., by new workers and firms in the case of a labor market. The major novelty of this approach is that the distribution of types in the market becomes an endogenous variable, which is jointly determined with equilibrium contracts. As frictions become small, we show that the least-cost separating contracts are always supported as an equilibrium outcome, regardless of the distribution of types among entrants. Moreover, we derive conditions under which this outcome is also unique.     

Don’t let your robots grow up to be traders: Artificial intelligence, human intelligence, and asset-market bubbles

Researchers who have examined markets populated by “robot traders” have claimed that the high level of allocative efficiency observed in experimental markets is driven largely by the “intelligence” implicit in the rules of the market. Furthermore, they view the ability of agents (artificial or human) to process information and make rational decisions as unnecessary for the efficient operation of markets. This paper presents a new series of market experiments that show that markets populated with standard robot traders are no longer efficient if time is a meaningful element, as it is in all asset markets. While simple two-season markets with human subjects reliably converge to an efficient equilibrium, markets with minimally intelligent robot traders fail to attain this equilibrium. Instead, these markets overshoot the equilibrium and then crash below it. In addition to firmly establishing the role of trader intelligence in asset-market equilibrium, these experiments also provide insights into why bubbles and crashes are consistently observed in many asset-market laboratory experiments using human subjects.     

Costly risk verification without commitment in competitive insurance markets

This paper analyzes the equilibrium of an insurance market where applicants for insurance have a duty of good faith when they reveal private information about their risk type. Insurers can, at some cost, verify the type of insureds who file a claim and they are allowed to retroactively void the insurance contract if it is established that the policyholder has misrepresented his risk when the contract was taken out. However, insurers cannot precommit to their risk verification strategy. The paper analyzes the relationship between second-best Pareto-optimality and the insurance market equilibrium in a game theoretic framework. It characterizes the contracts offered at equilibrium, the individuals' contract choice as well as the conditions under which an equilibrium exists.     

Insurance,self-control,and contract flexibility

We study a competitive insurance market in which some consumers have too optimistic expectations regarding their future use of preventive measures. When contracts are long-term and inflexible, such naive consumers would increase the costs of insurance for low-risk consumers. The competitive insurance market therefore offers flexible contracts that allow for switching between different tariffs. Sophisticated consumers choose a partial insurance tariff and remain low-risks. Naive consumers choose the same tariff, but later switch to full insurance, and become high-risks. If there are sufficiently many naive consumers, they pay a transfer to sophisticated consumers (so that high-risks subsidize low-risks). In contrast, there are no such transfers when contracts are short-term. The model generates novel implications for the time frame of insurance contracts and insurance requirements.     

Non-discriminating renegotiation in a competitive insurance market

A variant of the Rothschild-Stiglitz model of a competitive insurance market is considered, where each uninformed firm is allowed to renegotiate the contracts that its customers initially sign, subject to the restriction that renegotiated contracts be offered to all the firm's customers. Such non-discriminating renegotiation is shown to weaken the profitability of cream skimming to the extent that there exists a unique equilibrium outcome. This outcome is that of Miyazaki and Spence i.e., the incentive-compatible pair of zero-profit contracts, if efficient; and the incentive-compatible, zero-profit pair of contracts maximizing low-risk utility, otherwise.     

Contracts and externalities: How things fall apart

A single principal interacts with several agents, offering them contracts. The crucial assumption of this paper is that the outside-option payoffs of the agents depend positively on how many uncontracted or “free” agents there are. We study how such a principal, unwelcome though he may be, approaches the problem of contract provision to agents when coordination failure among the latter group is explicitly ruled out. Two variants are considered. When the principal cannot re-approach agents, there is a unique equilibrium, in which contract provision is split up into two phases. In phase 1, simultaneous offers at good (though varying) terms are made to a number of agents. In phase 2, offers must be made sequentially, and their values are “discontinuously” lower: they are close to the very lowest of all the outside options. When the principal can repeatedly approach the same agent, there is a multiplicity of equilibria. In some of these, the agents have the power to force delay. They can hold off the principal's overtures temporarily, but they must succumb in finite time. In both models, despite being able to coordinate their actions, agents cannot resist an “invasion” by the principal and hold to their best payoff. It is in this sense that “things [eventually] fall apart”.     

Globally evolutionarily stable portfolio rules

The paper examines a dynamic model of a financial market with endogenous asset prices determined by short-run equilibrium of supply and demand. Assets pay dividends that are partially consumed and partially reinvested. The traders use fixed-mix investment strategies (portfolio rules), distributing their wealth between assets in fixed proportions. Our main goal is to identify globally evolutionarily stable strategies, allowing an investor to “survive,” i.e., to accumulate in the long run a positive share of market wealth, regardless of the initial state of the market. It is shown that there is a unique portfolio rule with this property—an analogue of the famous Kelly rule of “betting your beliefs.” A game theoretic interpretation of this result is given.     

Experimental evidence on coverage choices and contract prices in the market for corporate insurance

In this paper, we present experimental evidence on the effect adverse selection has on coverage choices and pricing in corporate insurance markets. Two sets of experimental data, each generated by experiments utilizing a specific parameterization of a corporate insurance decision, are presented to gauge these effects. In the first, subject behavior conforms to a unique equilibrium in which high risk firms choose higher coverage and contracts are priced accordingly. Insurers act competitively and convergence to equilibrium behavior is marked. In the second set, there is little evidence that subject behavior is consistent with either of the two equilibrium outcomes supported by the experimental setting—pooling by fully insuring losses and pooling by self insuring. JEL Classification C90, G14, G22 Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s10683-006-9152-y.     

Moral hazard contracts: Does one size fit all?

We show that firms' practice of anonymous contracts (“one-size-fits-all”) can be reconciled with standard agency theory if careers are marked by frequent transitions between employers, and agents have career concerns because complete long-term contracts are not feasible.     

Share contracts and macroeconomic externalities

Weitzman's analysis of the share economy contrasts fixed-wage and fixed-share contracts; this paper notes that neither is an optimal labor contract, rendering the comparison suspect. Given this comparison, though, share contracts may be superior to wage contracts in an economy characterized by a “macroeconomic externality,” whereby firm-level employment decisions affect the demand for other firms' goods.     

Abreu–Matsushima Mechanisms: Experimental Evidence

Abreu–Matsushima mechanisms can be applied to a broad class of games to induce any desired outcome as the unique rationalizable outcome. We conduct experiments investigating the performance of such mechanisms in two simple coordination games. In these games one pure-strategy equilibrium is “focal”; we assess the efficacy of Abreu–Matsushima mechanisms for implementing the other pure-strategy equilibrium outcome. Abreu–Matsushima mechanisms induce some choices consistent with the desired outcome, but more choices reflect the focal outcome. Moreover, “strengthening” the mechanism has a perverse effect when the desired outcome is a Pareto-dominated risk-dominated equilibrium.Journal of Economic LiteratureClassification Number: C7.     

High growth and low consumption in East Asia: How to improve welfare while avoiding financial failures

This paper analyzes certain policies that are typical of a number of rapidly growing East Asian countries in which a fixed exchange rate, combined with a surplus labor market, has made domestic assets relatively inexpensive, generating high rates of FDI as well as domestic capital formation. This “investment hunger” can lead to unanticipated declines in the returns to investment, and resulting financial insolvencies. Private consumption remains low and there are concerns that high savings rates cannot be sustained.We construct a dynamic general equilibrium model and apply it to a stylized Asian economy, loosely based upon China. We calibrate a benchmark equilibrium, and carry out various counterfactual simulations to analyze alternative policies, in particular tax cuts and exchange rate revaluations, as instruments in increasing private consumption while avoiding bank failures.     

Insurance with Frequency Trading: A Dynamic Analysis of Efficient Insurance Markets

This paper extends existing insurance results on the type of insurance contracts needed for insurance market efficiency to a dynamic setting. It introduces continuously open markets that allow for more efficient asset allocation. It also estimates the role of preferences and endowments in the classification of risks, which is done primarily in terms of the actuarial properties of the underlying risk process. The paper further extends insurability to include correlated and catastrophic events. Under these very general conditions the paper defines a condition that determines whether a small number of standard insurance contracts (together with aggregate assets) suffice to complete markets or one needs to introduce such assets as mutual insurance. Journal of Economic Literature Classification Numbers: D81, D99, G11.     

Labor Markets and Kaleidoscopic Comparative Advantage

Capturing the notion of kaleidoscopic comparative advantage ( Bhagwati, 1998 ), we show that international trade increases the volatility of profitability. In this framework, we address the labor market implications of an increase in openness, when insurance and credit markets are imperfect. With kaleidoscopic comparative advantage, trade raises the likelihood of firm shutdown and worker displacement, which, in equilibrium, affects wage contracts. In a simple model, we analyze the consequences for wage levels, earnings volatility, job instability, and income distribution, of the openness of previously nontraded industries to international trade.     

“Very Nice” trivial equilibria in strategic market games

Following Shapley [Theory of Measurement of Economic Externalities, Academic Press, New York, 1976], we study the problem of the existence of a Nash Equilibrium (NE) in which each trading post is either active or “legitimately” inactive, and we call it a Shapley NE. We consider an example of an exchange economy, borrowed from Cordella and Gabszewicz [Games Econ. Behav. 22 (1998) 162–169], which satisfies the assumptions of Dubey and Shubik [J. Econ. Theory 17 (1978) 1–20], and we show that the trivial equilibrium, the unique NE of the associated strategic market game, is not “very nice,” in the sense that it is not “legitimately” trivial. This result has the more general implication that, under the Dubey and Shubik's assumptions, a Shapley NE may fail to exist.     

Welfare costs of reclassification risk in the health insurance market

We assess the quantitative importance of reclassification risk in the US health insurance market. Reclassification risk arises because the health conditions of individuals evolve over time, while a typical health insurance contract only lasts for one year. Thus, a change in the health status can lead to a significant change in the health insurance premium. We measure welfare gains from introducing explicit insurance against this risk in the form of guaranteed renewable health insurance contracts. We find that in the current institutional environment individuals are well-sheltered against reclassification risk and they only moderately gain from having access to these contracts. More specifically, we show that employer-sponsored health insurance and public means-tested transfers play an important role in providing implicit insurance against reclassification risk. If these institutions are removed, the average welfare gains from having access to guaranteed renewable contracts exceed 4% of the annual consumption.     

Credit quality, the intensity of regulation and the segmentation of debt markets

Some debt markets have a “competitive advantage” over others due to easier regulatory requirements. Our model explains changes in the market shares of different debt markets. In particular, borrowers may choose between highly regulated and relatively unregulated placement of debt so as to minimize borrowing costs. Borrowers in the highly regulated market incur higher regulatory cost, but are also able to signal accurately their true risk class. In unregulated markets there is an asymmetric information problem. This results in an equilibrium where the debt market is segmented between less regulated and other, more strictly regulated, placements. Raising regulatory costs will lead to an expansion of the market share of unregulated debt. It will also lead to an increase in the overall default rate on corporate debt.     

Microeconomic modeling of parallel markets: The case of agricultural goods in the USSR

In a centrally planned economy, non-market-clearing prices fixed by the state cannot be used directly to estimate consumer behavior models. This paper represents an attempt to overcome this problem by utilizing prices in a parallel “free” market. An equilibrium model incorporating parallel markets is discussed and a demand curve arising from this model is estimated using data for the markets for meat and milk in the USSR. the price and income elasticities of demand for these goods are found to be significantly higher than those estimated for the United States.     

论巨灾期权及其演进

巨灾期权是以巨灾损失指数为基础而设计的期权合同,是保险公司通过在期权市场上缴纳一定期权费以购买在未来一段时间内的一种价格选择权。本文旨在对巨灾期权及其演进进行系统考察,以期对其有更为全面的认识。本文回顾了巨灾期权的市场发展;分析了ISO,PCS,GCCI和CHI四种指数为基础的巨灾期权产品和运作原理,考察了这四种巨灾指数及其产品的演进。     

Endogenous Categorization in Insurance

This paper analyzes the welfare properties of equilibrium when insurers use observable actions to classify consumers into different risk categories, and consumers' choice is influenced by the insurance market consequences of their actions. Specifically, we analyze this problem at the example of a car insurance market, in which individual preferences over car types are correlated with risk type and used by insurance firms for ratemaking. Equilibrium premiums for each car are determined by the losses that it generates. Consumers take insurance premiums into account when deciding which car to buy. This creates an incentive to buy the car that is preferred by more low risk individuals. From a utilitarian point of view, this incentive is excessive. Depending on parameters, it may even be possible to construct a tax‐subsidy scheme with balanced budget that Pareto improves on the market equilibrium.