Kfir Eliaz

Indifference or indecisiveness? Choice-theoretic foundations of incomplete preferences

Abstract A commonly held belief in economics is that an individuals preferences that are revealed by her choices must be complete. This paper takes issue with this position by showing that one may be able to distinguish between indifference and indecisiveness of an agent upon observing her choice behavior. We relax the standard Weak Axiom of Revealed Preferences (WARP) and show that a potent theory of individual choice (with and without risk) can be founded on this weaker axiom when it is coupled with some other standard postulates. The most notable features here are that an agent is allowed to be indifferent between certain alternatives and indecisive about others. Moreover, an outside observer can identify which of these actually occur upon examining the (observable) choice behavior of the decision maker. As an application, we also show how our theory may be able to cope with the classical preference reversal phenomenon.

Can Anticipatory Feelings Explain Anomalous Choices of Information Sources

The well-being of agents is often directly affected by their beliefs, in the form of anticipatory feelings such as anxiety and hopefulness. Economists have tried to model this effect by introducing beliefs as arguments in decision makers vNM utility function. One might expect that such a model would be capable of explaining anomalous attitudes to information that we observe in reality. We show that the model has several shortcomings in this regard, as long as Bayesian updating is retained.

Group Decision-Making in the Shadow of Disagreement

A model of group decision-making is studied, in which one of two alternatives must be chosen. While group members differ in their valuations of the alternatives, everybody prefers agreement to disagreement. Our model is distinguished by three features: private information regarding valuations, varying intensities in the preference for one outcome over the other, and the option to declare neutrality in order to avoid disagreement. We uncover a variant on the ‘tyranny of the majority’: there is always an equilibrium in which the majority is more aggressive in pushing its alternative, thus enforcing their will via both numbers and voice. Under general conditions, however, an aggressive minority equilibrium inevitably makes an appearance, provided that the group is large enough. The notable exception is the special case of unanimity rule: we show that aggressive minority equilibria may never exist irrespective of group size. Aggressive minority equilibria invariably display a ‘tyranny of the minority’: it is always true that the increased aggression of the minority more than compensates for smaller numbers, leading to the minority outcome being implemented with larger probability than the majority alternative. We fully characterize the asymptotic behavior of this model as group size becomes large, and show that all equilibria must converge to one of three possible limit outcomes.

Nash equilibrium when players account for the complexity of their forecasts

Nash equilibrium is often interpreted as a steady state in which each player holds the correct expectations about the other players` behavior and acts rationally. This paper investigates the robustness of this interpretation when players` preferences are affected by their forecasts about the other players. In particular, I analyze the case of lexicographic preferences in which the simplicity of forecasts is secondary to material payoffs.

Creating competition out of thin air: an experimental study of right-to-choose auctions

This paper presents an experimental study of a mechanism that is commonly used to sell multiple heterogeneous goods. The novel feature of this procedure is that instead of selling each good in a separate auction, the seller executes a single auction in which buyers, who may be interested in completely different goods, compete for the right to choose a good. We provide experimental evidence that a Right-to-Choose (RTC) auction can generate more revenue than the theoretically optimal auction. Moreover, in contrast to the optimal auction, the RTC auction is approximately efficient in the sense that the surplus it generates is close to the maximal one. Furthermore, a seller who would like to retain some of his goods can generate more revenue with a restricted RTC auction in which not all rights-to-choose are sold, than with the theoretically optimal auction.

Bargaining over bets

When two agents hold different priors over an unverifiable state of nature, which affects the outcome of a game they are about to play, they have an incentive to bet on the games outcome. We pose the following question: what are the limits to the agents ability to realize gains from such speculative bets when their priors are private information? We apply a mechanism design approach to this question. We characterize interim-efficient bets and discuss their implementability in terms of the underlying games payoff structure. In particular, we show that as the costs of unilaterally manipulating the bets outcome become more symmetric across states and agents, implementation becomes easier.