Dynamic versus one-period completeness in event-tree security markets

We show that in event-tree security markets dynamic completeness does not coincide with one-period completeness unless the law of one price is explicitely assumed. We do so by means of a simple example of a dynamically complete market with an incomplete one-period sub-market.     

Arbitrage and equilibrium in strategic security markets

Summary. In view of the fundamental price taking hypothesis, arbitrage is never compatible with equilibrium in Walrasian markets because the existence of an arbitrage opportunity in a competitive situation always leads to unbounded arbitrage activity. In strategic markets however, the mere effort of individuals to profit alters market clearing prices and thus distorts arbitrage opportunities as well. This observation suggests a different relationship between arbitrage and equilibrium, than in the competitive model. Indeed, we show that in such markets a spread between the cost of a portfolio and its returns is compatible with equilibrium. We provide an example of an equilibrium where a resourceless individual holds a portfolio with zero cost and positive return in every state. We further demonstrate via an asymptotic result, that no arbitrage is intimately related to price taking behaviour.Received: 8 September 2001, Revised: 6 March 2003, JEL Classification Numbers: G12, D4, D5, D52. Correspondence to: Leonidas C. Koutsougeras     

商业银行体系稳定性与竞争程度之测度研究

银行业的市场结构、竞争程度对银行的稳定性究竟起什么样的作用，是现今国际上讨论较多、但尚未达成一致意见的问题。运用相关数据对中国银行业情况进行实证分析，可得出集中的市场结构、和缓的竞争更有利于银行业稳定的结果。     

Capacity constrained firms in (labor) markets with adverse selection

Summary. We discuss a competitive (labor) market where firms face capacity constraints and individuals differ according to their productivity. Firms offer two-dimensional contracts like wage and task level. Then workers choose firms and contracts. Workers might be rationed if the number of applicants exceeds the capacity of the firm. We show that under reasonable assumptions on the distribution of capacity an equilibrium in pure strategies (by the firms) exists. This result stands in contrast to the case of unlimited capacity. The utility level is uniquely determined in equilibrium. No rationing occurs in equilibrium, but it does off the equilibrium path. Received: December 29, 1999; revised version: November 30, 2000     

Aggregation under complete markets

This paper proves a complete market aggregation result for a multiple good economy in which the consumers have time-additive, von Neumann–Morgenstern utility functions. This result applies to all concave intraperiod functions, and provides a contrast to many of the results in the microeconomics literature which depend on such stringent assumptions as linear Engel curves.     

On Rothschild–Stiglitz as Competitive Pooling

Dubey and Geanakoplos (Q J Econ 117:1529–1570, 2002) have developed a theory of competitive pooling, which incorporates adverse selection and signaling into general equilibrium. By recasting the Rothschild–Stiglitz model of insurance in this framework, they find that a separating equilibrium always exists and is unique. We prove that their uniqueness result is not a consequence of the framework, but rather of their definition of refined equilibria. When other types of perturbations are used, the model allows for many pooling allocations to be supported as such: in particular, this is the case for pooling allocations that Pareto dominate the separating equilibrium.     

Proactive planning and valuation of transmission investments in restructured electricity markets

Traditional methods of evaluating transmission expansions focus on the social impact of the investments based on the current generation stock which may include firm generation expansion plans. In this paper, we evaluate the social welfare implications of transmission investments based on equilibrium models characterizing the competitive interaction among generation firms whose decisions in generation capacity investments and production are affected by both the transmission investments and the congestion management protocols of the transmission system operator. Our analysis shows that both the magnitude of the welfare gains associated with transmission investments and the location of the best transmission expansions may change when the generation expansion response is taken into consideration. We illustrate our results using a 30-bus network example. An erratum to this article can be found at     

Aggregation of heterogenous beliefs,asset pricing,and risk sharing in complete financial markets

Given a competitive equilibrium in complete asset markets, we propose a method that aggregates heterogeneous individual beliefs into a single “market probability,” which, if commonly shared by investors, generates the same marginal valuation of assets by the market as well as by each individual investor. As a result of the aggregation process, the market portfolio may have to be scalarly adjusted, upward or downward, a reflection of an aggregation bias due to the diversity of beliefs. From a dual viewpoint, the standard construction of an expected utility-maximizing aggregate investor designed to represent the economy in equilibrium, is shown to be also valid in the case of heterogeneous beliefs, modulo the above scalar adjustment of the market portfolio, thereby generating an Adjusted version of the Consumption based Capital Asset Pricing Model (ACCAPM). We analyze how the allocation of aggregate and individual risks relates to deviations of individual beliefs from the aggregate market probability. Finally, we identify the channels through which the distribution of beliefs and other microeconomic characteristics (incomes, attitudes toward risk) across investors impact the pricing of risky assets an may contribute to explaining the equity premium puzzle.     

Sequentially complete markets remain incomplete

We show by means of an example that the result of Arrow [Arrow, K.J. (1953), Le rôle des valeurs boursières pour la répartition la meilleure des risques, Econométrie, 41–47, CNRS, Paris; translated as The role of securities in the optimal allocation of risk bearing, Review of Economic Studies, 31, 91–96] is problematic when there exist multiple equilibrium continuations to the initial-period component of an intertemporal equilibrium.     

On games with identical equilibrium payoffs

Summary. This paper compares the sets of Nash, coalition- proof Nash and strong Nash equilibrium payoffs of normal form games which are closely related. We propose sufficient conditions for equivalent or closely related games to have identical sets of equilibrium payoffs. Received: April 23, 1999; revised version: November 23, 1999     

Market power, survival and accuracy of predictions in financial markets

In a standard General Equilibrium framework, we consider an agent strategically using her large volume of trade to influence asset prices to increase her consumption. We show that, as in Sandroni (Econometrica 68:1303–1341, 2000) for the competitive case, if markets are dynamically complete and some general conditions on market preferences are met then this agent’ long-run consumption will vanish if she makes less accurate predictions than the market, and will maintain her market power otherwise. We thus argue that the Market Selection Hypothesis extends to this situation of market power, in contrast to Alchian (J Pol Econ 58:211–221, 1950) and Friedman (Essays in Positive Economics, University of Chicago Press, Chicago, 1953) who claimed that this selection was solely driven by the competitiveness of markets. I would like to thank T. Hens, A. Kirman and A. Sandroni for many stimulating conversations and encouragements. Two anonymous referees also provided very valuable comments.     

基于众包的开放式创新研究:现状与发展方向

首先界定了开放式创新与众包的概念,并澄清了二者之间的关系,在此基础上确定了文献搜集范围。通过内容分析发现,相关文献分别基于参与者、发起者以及创新平台3种视角,主要围绕Who、Why、What、How4方面的主题展开研究。基于这种发现,对文献分别按照研究主题进行了梳理,分析了目前研究中存在的不足,并指出了未来可能的发展方向。     

Allowing communities to trade in imperfectly competitive pollution-permit markets

Citizens and organizations representing them play an increasingly important role in markets for environmental quality, but much remains to be learned about how their participation affects these markets. We analyze the effects of allowing a community of citizens to trade pollution permits in an imperfectly competitive permit market. Allowing the community to trade directly reveals its preferences, which enhances welfare. However, community participation may also exacerbate distortions due to market power, even though the community itself trades competitively. Including the community in permit distribution may exacerbate market power distortions by affecting a dominant trader’s propensity to participate in the permit market. Second, the community’s demand/supply for permits may be more inelastic than other traders and worsen distortions due to market power. We illustrate in an example that these negative effects on competition can dominate the positive effect from preference revelation through the market place.      

Competitive equilibrium when preferences change over time

Summary. We show the existence of a competitive equilibrium in an economy with many consumers whose preferences may change over time. The demand correspondence of an individual consumer is determined by the set of subgame-perfect equilibrium outcomes in his intrapersonal game. For additively separable preferences with concave period utility functions that are unbounded above, this demand correspondence will satisfy the usual boundary conditions. Whenever consumers can recall their own mixed actions, this correspondence is convex-valued. This ensures the existence of a symmetric competitive equilibrium.Received: 29 July 2004, Revised: 17 November 2004, JEL Classification Numbers: D51, D91, C73. Correspondence to: Thomas MariottiWe thank Michele Piccione for useful comments and suggestions. The views expressed herein are those of the authors and not necessarily those of the Federal Reserve Bank of Minneapolis or the Federal Reserve System.     

Optimal truncation in matching markets

Although no stable matching mechanism can induce truth-telling as a dominant strategy for all participants (Roth, 1982), recent studies have presented conditions under which truthful reporting by all agents is close to optimal (Immorlica and Mahdian, 2005, Kojima and Pathak, 2009, Lee, 2011). Our results demonstrate that in large, uniform markets using the Men-Proposing Deferred Acceptance Algorithm, each woman's best response to truthful behavior by all other agents is to truncate her list substantially. In fact, the optimal degree of truncation for such a woman goes to 100% of her list as the market size grows large. In general one-to-one markets we provide comparative statics for optimal truncation strategies: reduction in risk aversion and reduced correlation across preferences each lead agents to truncate more. So while several recent papers focused on the limits of strategic manipulation, our results serve as a reminder that without pre-conditions ensuring truthful reporting, there exists a potential for significant manipulation even in settings where agents have little information.     

Equilibrium in a Market Game

This paper studies the equilibrium of an exchange economy with the same number of agents and commodities. It is shown that under rather mild conditions on demand the market have a price equilibrium—independently of the divisibility of the commodities. The result extends Gale’s equilibrium theorem for indivisible commodities to the case where some commodities are perfectly divisible. The proof is based on a topological lemma contained in previous paper of one of the authors.     

Cheating in markets: A laboratory experiment

We develop a two-market model under three conditions: autarky, frictionless free trade, and free trade with cheating. With cheating, buyers can underpay by π% in cross-market trades and sellers can deliver π% of full value. We solve for competitive equilibrium with cheating and obtain novel testable predictions on price, volume and surplus. We test these in a laboratory experiment using parameters intended to challenge the theory. The results are generally consistent with competitive equilibrium. We find evidence of price unification, market segmentation, a cross-market volume of trade lower under cheating than in frictionless free trade, but a higher overall volume.     

Mixed markets and crime

This paper specifies and solves a two-stage, game theoretic model of a mixed market for crime control. In the first stage of the model, private targets and the government choose levels of policing. In the second stage, criminals choose targets and the severity of the crimes that they commit.The paper's key results are as follows. First, private policing can both divert crime to targets that lack private protection and also increase the severity of the crime that these less-protected targets suffer. Second, an increase in private policing reduces the aggregate expenditure on traditional policing. This is an instance of a political incentive externality, where private policing affects the objective function of the government. Specifically, it reduces the level of traditional policing that is consistent with the Samuelson condition for efficient provision of a public good. Third, the substitution of private for public policing carries with it a change in the technology of policing. In effect, private policing leads to a shift from enforcement and punishment towards monitoring and target hardening. This, in turn, may lead to an increase in the severity of crime. Fourth, the mixed policing equilibrium is inefficient, and, in some situations, mixing may reduce the utility of all targets.     

Asset market equilibrium with short-selling and differential information

We introduce differential information in the asset market model studied by Cheng J Math Econ 20(1):137–152,1991, Dana and Le Van J Math Econ 25(3):263–280,1996 and Le Van and Truong Xuan J Math Econ 36(3): 241–254, 2001. We prove an equilibrium existence result assuming that the economy’s information structure satisfies the conditional independence property. If private information is not publicly verifiable, agents have incentives to misreport their types and therefore contracts may not be executed in the second period. We also show that under the conditional independence property equilibrium contracts are always executable.     

Time-inconsistent preferences in a general equilibrium model

This paper introduces time-inconsistent preferences in a multicommodity general equilibrium framework with incomplete markets. The standard concept of competitive equilibrium is extended in order to allow for changes in intertemporal preferences. Depending on whether or not agents recognize that their intertemporal preferences change, agents are called sophisticated or naïve. This paper presents competitive equilibrium notions for economies with naïve agents and economies with sophisticated agents and provides assumptions under which both types of equilibria exist. Surprisingly, the set of naïve equilibria in societies populated by time-consistent households is not allocationally equivalent to the set of competitive equilibria. For sophisticated equilibria, the equivalence holds. Time-inconsistency also raises conceptual issues about the appropriate concept of efficiency. Choices have to be made concerning the incorporation of future preferences and the appropriate instruments to create Pareto improvements. For both naïve and sophisticated societies, we present four possible efficiency concepts. Suitable conditions are specified for which both naïve and sophisticated equilibria satisfy appropriate efficiency concepts.