Efficient and stable collective choices under gregarious preferences

We consider collective choice problems where a set of agents have to choose an alternative from a finite set and agents may or may not become users of the chosen alternative. An allocation is a pair given by the chosen alternative and the set of its users. Agents have gregarious preferences over allocations: given an allocation, they prefer that the set of users becomes larger. We require that the final allocation be efficient and stable (no agent can be forced to be a user and no agent who wants to be a user can be excluded). We propose a two-stage sequential mechanism whose unique subgame perfect equilibrium outcome is an efficient and stable allocation which also satisfies a maximal participation property.     

Herding and bank runs

Traditional models of bank runs do not allow for herding effects, because in these models withdrawal decisions are assumed to be made simultaneously. I extend the banking model to allow a depositor to choose his withdrawal time. When he withdraws depends on his consumption type (patient or impatient), his private, noisy signal about the quality of the bank's portfolio, and the withdrawal histories of the other depositors. Some of these runs are efficient in that the bank is liquidated before the portfolio worsens. Others are not efficient; these are cases in which the herd is misled.     

Market design with endogenous preferences

This paper explores the interdependence between market structure and an important class of cognitive biases. Starting with a familiar bilateral monopoly framework, we characterize the endogenous emergence of preference distortions during bargaining which cause negotiators to perceive their private valuations differently than they would outside the adversarial negotiation context. Using this model, we then demonstrate how a number of external interventions in the structure and/or organization of market interactions (occurring before trade, after trade, or during negotiations themselves) can profoundly alter the nature of these dispositions. Our results demonstrate that many such interventions frequently (though not always) share qualitatively similar characteristics to market interventions that are often proposed for overcoming more conventional forms of market failure. Nevertheless, our analysis underscores the importance of understanding the precise link between cognitive failures and market structure prior to the implementation of any particular proposed reform.     

Repeated games with present-biased preferences

We study infinitely repeated games with perfect monitoring, where players have β-δ preferences. We compute the continuation payoff set using recursive techniques and then characterize equilibrium payoffs. We then explore the cost of the present-time bias, producing comparative statics. Unless the minimax outcome is a Nash equilibrium of the stage game, the equilibrium payoff set is not monotonic in β or δ. Finally, we show how the equilibrium payoff set is contained in that of a repeated game with smaller discount factor.     

羊群效应对股指波动率的影响分析

投资者行为对资本市场的稳定性影响是行为金融学关注的热点问题之一。本文以浦发银行股票为研究对象,首先,利用羊群行为的程度作为度量羊群行为的数量标准,通过建立ARCH模型,对浦发银行股票是否存在羊群效应进行统计检验,结果表明浦发银行股票存在显著的羊群效应。其次,通过建立线性回归模型分析了羊群行为对股票波动性的影响。实证研究表明,股票的羊群行为程度与股票指数波动率成正相关关系。     

A Social-Psychological Perspective on Herding in Stock Markets

A social-psychological perspective conceives of herding in stock markets as informative social influence resulting from heuristic or systematic information processing. In three laboratory experiments employing undergraduates we apply this perspective to investigate factors that prevent herd influence that would lead to inaccurate predictions of stock prices. In Experiment 1, we show that an economic reward for making the same predictions as the herd increases the influence of a majority but not the influence of a minority, and that an individual economic reward for making accurate predictions reduces the influence of the majority. In Experiment 2, we show a reduced influence of a majority herd's inaccurate predictions when requiring assessments of the accuracy of the majority herd´s predictions as compared to requiring judgments of their consistency. Experiment 3 shows that a lower volatility of stock prices reduces the influence of a majority herd´s inaccurate predictions.     

Finitely repeated games with social preferences

A well-known result from the theory of finitely repeated games states that if the stage game has a unique equilibrium, then there is a unique subgame perfect equilibrium in the finitely repeated game in which the equilibrium of the stage game is being played in every period. Here I show that this result does in general not hold anymore if players have social preferences of the form frequently assumed in the recent literature, for example in the inequity aversion models of Fehr and Schmidt (Quartely Journal of Economics 114:817–868, 1999) or Bolton and Ockenfels (American Economic Review 100:166–193, 2000). In fact, repeating the unique stage game equilibrium may not be a subgame perfect equilibrium at all. This finding should have relevance for all experiments with repeated interaction, whether with fixed, random or perfect stranger matching.     

Optimality of workfare with heterogeneous preferences

With the standard non-linear income taxation framework with heterogeneity of preferences, in this paper the optimality of workfare as a screening tool is examined. It is assumed that workfare does not serve as a human capital investment, participation is mandatory, and administrative costs are negligible. Imposing alternative cardinalizations on individuals utilities allows for the possibility that the government optimally redistributes income to or from high disutility of labour individuals. Under either case, it is never optimal to impose workfare on these individuals. It is also shown that non-productive workfare can be an efficient policy tool, in contrast to the results found in Besley and Coate (1995), Brett (1998), and Beaudry and Blackorby (1997). JEL Classification: H21, H23
Optimalité du workfare en présence de préférences hétérogènes. L'auteur examine l'timalité du workfare en tant qu'instrument de tamisage à l'aide du cadre conceptuel traditionnel d'imposition non-linéaire des revenus en présence de préférences hétérogènes. On postule que le workfare n'est pas un processus d'investissement en capital humain, que la participatioun est obligatoire, et que les coûts d'administration sont négligeables. Quand on postule aussi des utilités cardinales différentes pour les individus, il devient possible pour le gouvernement de redistribuer optimalement les revenus en faveur ou au détriment des individus pour qui le travail a une très grande désutilité. Dans l'un et l'autre cas, on montre que le workfare n'est jamais une politique optimale. On montre aussi que le workfare dans des activités non-productives peut être un instrument de politique publique efficient, contrairement a ce qu'affirment Besley et Coate (1995), Brett (1998) et Beaudry et Blackorby (1997).     

Optimal stopping with dynamic variational preferences

We solve optimal stopping problems in uncertain environments for agents assessing utility by virtue of dynamic variational preferences as in Maccheroni, Marinacci and Rustichini (2006) [16] or, equivalently, assessing risk in terms of dynamic convex risk measures as in Cheridito, Delbaen and Kupper (2006) [4]. The solution is achieved by generalizing the approach in Riedel (2009) [21] introducing the concept of variational supermartingales and variational Snell envelopes with an accompanying theory. To illustrate results, we consider prominent examples: dynamic multiplier preferences and a dynamic version of generalized average value at risk introduced in Cheridito and Tianhui (2009) [5].     

Weighted congestion games with separable preferences

Players in a congestion game may differ from one another in their intrinsic preferences (e.g., the benefit they get from using a specific resource), their contribution to congestion, or both. In many cases of interest, intrinsic preferences and the negative effect of congestion are (additively or multiplicatively) separable. This paper considers the implications of separability for the existence of pure-strategy Nash equilibrium and the prospects of spontaneous convergence to equilibrium. It is shown that these properties may or may not be guaranteed, depending on the exact nature of player heterogeneity.     

Overriding consumer preferences with energy regulations

The recent wave of enacted and proposed U.S. energy regulations imposes energy efficiency standards on light bulbs, appliances, and motor vehicles based on the unsupported assumption that consumers and firms are irrational and that energy efficiency should be the paramount concern. The regulatory analyses do not document these purported failures in consumer choices or firms’ energy utilization decisions with any empirical evidence. The preponderance of the benefits that agencies claim for the regulations is derived from private benefits to consumers and firms attributable to lower energy costs. Without these benefits, the regulatory costs would greatly exceed the benefits. The regulatory analyses consider only mandates as a means of achieving energy-efficiency improvements and ignore other policy options.     

价格调整机制对羊群行为影响的实验研究

由于在现实证券市场中很难观测行为主体的信息结构,实证方法在对羊群行为的理论模型进行直接检验时存在诸多困难,导致羊群行为的实证检验只具有纯粹的统计学意义。实验经济学可以控制行为主体的私有信息及市场交易的公共信息,因此可以对理论模型进行直接检验。文章采用实验经济学的方法考察价格调整机制对羊群行为的影响,在检验理论的同时,发现价格调整机制降低了信息串联的比例和实际决策的效率,增加了非理性决策的比例。     

Herding,contrarianism and delay in financial market trading

Herding and contrarian behaviour are often-cited features of real-world financial markets. Theoretical models of continuous trading that study herding and contrarianism, however, usually do not allow traders to choose when to trade or to trade more than once. We present a large-scale experiment to explore these features within a tightly controlled laboratory environment. Herding and contrarianism are more pronounced than in comparable studies that do not allow traders to time their decisions. Traders with extreme information tend to trade earliest, followed by those with information conducive to contrarianism, while those with the theoretical potential to herd delay the most. A sizeable fraction of trades is clustered in time.     

Herding in Chinese stock markets: a nonparametric approach

The paper reports new evidence of herding in the Chinese A-type and B-type markets by employing nonparametric kernel regression. We find statistically significant evidence of herding in A-type market under both extreme high and low market returns. Herding in B-type market, which predominantly consists of foreign investors, indicates only weak evidence of herding. We do not find any statistically significant evidence of herding in the pre-2001 sample of B-type market, when only foreign investors could do the trading. Lack of knowledge and experience of local investors may be attributed to the presence of herd behaviour in the Chinese markets.     

On preferences with infinitely many subjective states

Models with subjective state spaces have been extremely useful in capturing novel psychological phenomena that consist of both a preference for flexibility and for commitment. Interpreting the utility representations of preferences as capturing these phenomena requires one to use the notion of a sign of a state. For linear preferences, we completely characterise the sign of a state in terms of its analytic representation as an integral with respect to a signed measure. In models with finitely many states, a state is either positive or negative, but never both. We show that in models with infinitely many states, a state can be both positive and negative. Thus, models with finitely many states may not capture all the behavioural features of an infinite model. Our methods are also useful in constructing utility functionals over menus with desired local properties.     

Representing roommates’ preferences with symmetric utilities

In the context of the stable roommates problem, it is shown that acyclicity of preferences is equivalent to the existence of symmetric utility functions, i.e. the utility of agent i when matched with j is the same as j's utility when matched with i.     

Nash equilibrium in games with incomplete preferences

Summary. This paper investigates Nash equilibrium under the possibility that preferences may be incomplete. I characterize the Nash-equilibrium-set of such a game as the union of the Nash-equilibrium-sets of certain derived games with complete preferences. These games with complete preferences can be derived from the original game by a simple linear procedure, provided that preferences admit a concave vector-representation. These theorems extend some results on finite games by Shapley and Aumann. The applicability of the theoretical results is illustrated with examples from oligopolistic theory, where firms are modelled to aim at maximizing both profits and sales (and thus have multiple objectives). Mixed strategy and trembling hand perfect equilibria are also discussed.Received: 22 September 2003, Revised: 24 June 2004, JEL Classification Numbers: D11, C72, D43.I would like to thank Jean-Pierre Benôit, Juan Dubra, Alejandrio Jofre, Debraj Ray, Kim-Sau Chung and the seminar participants at NYU and at the Universidad de Chile for their comments. I am most grateful to Efe Ok, for his comments, criticism, suggestions and questions.     

Lagrangean conditions for consumers with nonrepresentable preferences

A Lagrangian characterization of the solutions of the consumer problem is provided when preferences are not representable by a continuous utility function.     

The swing voter's curse with adversarial preferences

We analyze voting behavior in a large electorate in which voters have adversarial state-contingent preferences with incomplete information about the state of the world. We show that one type of voter can suffer from the swing voter's curse à la Feddersen and Pesendorfer [The swing voter's curse, Amer. Econ. Rev. 86 (1996) 408-424], and go on to characterize the symmetric Nash equilibria of this model under different parameter values. We prove that unlike settings with nonadversarial preferences, there are equilibria in which in one state of the world, a minority-preferred candidate almost surely wins the election and thus the election may fail to correctly aggregate information. Indeed, we show that the fraction of the electorate dissatisfied with the result can be as large as .