Eyal Winter

Incentives and Discrimination

Optimal incentive mechanisms may require that agents are rewarded differentially even when they are completely identical and are induced to act the same. We demonstrate this point by means of a simple incentive model where agents’ decisions about effort exertion is mapped into a probability that the project will succeed. We give necessary and sufficient conditions for optimal incentive mechanisms to be discriminatory. We also show that full discrimination across all agents is required if and only if the technology has increasing return to scale. In the non-symmetric framework we show that negligible differences in agents’ attributes may result in major differences in rewards in the unique optimal mechanism.

Voting and Vetoing

The consequences of veto power in committees is analyzed using the appro ach of noncooperative bargaining theory. It is first shown that in equilibrium nonveto players do not share in the benefits gained by the decision making of the committee, that is, in every equilibrium outcome of the bargaining game, nonveto players earn zero. Some measures for reducing the excessive power of veto members in committees are analyzed. Specifically, I study the effects of imposing a deadline on negotiations and of expanding the committee by increasing the number of nonveto players. Quantitative results are given for the case of the UN Security Council.

Subscription mechanisms for network formation

We analyze a model of network formation where the costs of forming links are publicly known but an individuals benefits are not known to the social planner. The objective is to design a mechanism which not only ensures that an efficient network always forms in equilibrium but also ensures that the resulting net payoffs to the agents are equitable. We propose two mechanisms towards this end; in the first, agents announce sequentially the set of players with whom they wish to form links and a cost contribution. We show that all subgame perfect equilibria of this game result in the formation of an efficient network but the resulting net payoffs are asymmetric. The second mechanism corrects this asymmetry through a two-stage variant of the first mechanism. We also discuss an extension of the basic model to cover the case of directed graphs and give conditions under which the proposed mechanisms are immune to deviations by coalitions.

Coordination and Learning Behavior in Large Groups with Asymmetric Players

We study a class of large-group, noncooperative, iterated market entry games with complete information, binary choices, and asymmetric players in which the incentive of each player to enter the market decreases the larger the number of entrants. Experimental results from two different studies show remarkable coordination on the aggregate level, which is accounted for successfully by the Nash equilibrium solution. The equilibrium solution is less successful in accounting for the differences among types of players with differential entry costs or differences among players of the same type. Rather, the behavioral patterns observed on the aggregate level are accounted for by a reinforcement-based learning model postulating an initial distribution of individual cutoff points. These cutoff points are assumed to change over time, at a decreasing rate, as a joint function of the decision and outcome of the preceding period. Journal of Economic Literature Classification Numbers: C7, D5, D8.

The Demand Commitment Bargaining and Snowballing Cooperation

SummaryA multi-person bargaining model based on sequential demands is studied for coalitional games with increasing returns to scale for cooperation. We show that for such games the (subgame perfect) equilibrium behavior leads to a payoff distribution which approaches the Shapley value as the money unit approaches 0. Subgame consistency and strategic equilibria are the main tools used in the analysis. The model is then applied to study a problem of public good consumption.

Stability and Segregation in Group Formation

This paper presents a model of group formation based on the assumption that individuals prefer to associate with people similar to them. It is shown that, in general, if the number of groups that can be formed is bounded, then a stable partition of the society into groups may not exist. A partition is defined as stable if none of the individuals would prefer be in a different group than the one he is in. However, if individuals’ characteristics are one-dimensional, then a stable partition always exists. We give sufficient conditions for stable partitions to be segregating (in the sense that, for example, low-characteristic individuals are in one group and high-characteristic ones are in another) and Pareto efficient. In addition, we propose a dynamic model of individual myopic behavior describing the evolution of group formation to an eventual stable, segregating, and Pareto efficient partition.

Interactions between Workers and the Technology of Production: Evidence from Professional Baseball

This paper shows that workers can affect the productivity of their coworkers based on income maximization considerations, rather than relying on behavioral considerations such as peer pressure, social norms, and shame. We show that a workers effort has a positive effect on the effort of coworkers if they are complements in production, and a negative effect if they are substitutes. The theory is tested using a panel data set of baseball players from 1970 to 2003. The results are consistent with the idea that the effort choices of workers interact in ways that are dependent on the technology of production.

Bargaining with an agenda

Gradual bargaining is represented by an agenda: a family of increasing sets of joint utilities, parameterized by time. A solution for gradual bargaining specifies an agreement at each time. We axiomatize an ordinal solution, i.e., one that is covariant with order-preserving transformations of utility. It can be viewed as the limit of step-by-step bargaining in which the agreement of the last negotiation becomes the disagreement point for the next. The stepwise agreements may follow the Nash solution, the Kalai–Smorodinsky solution or many others and still yield the ordinal solution in the limit.

The principle of balanced contributions and hierarchies of cooperation

The principle of balanced contributions has appeared repeatedly in the literature on the Shapley value. This principle is akin to the reciprocity properties shared by almost all cooperative solution concepts. We provide a new axiomatization for the level structure value. This axiomatization has the advantage that it can be applied to many important subdomains of TU games. We use the Hart-Mas-Colell potential function as a tool to prove our main result, and establish another interesting characterization for the value as a by-product.

Experimental study of repeated team-games

Abstract We report an experiment in which the Intergroup Prisoners Dilemma (IPD) game was contrasted with a structurally identical (single-group) Prisoners Dilemma (PD). The games were played repeatedly for 40 rounds. We found that subjects were initially more likely to cooperate in the IPD game than in the PD game. However, cooperation rates decreased as the game progressed and, as a result, the differences between the two games disappeared. This pattern is consistent with the hypothesis that subjects learn the structure of the game and adapt their behavior accordingly. Computer simulations based on a simple learning model by Roth and Erev (Learning in extensive-form games: Experimental data and simple dynamic models in the intermediate term, Games and Economic Behavior 8, 164–212, 1995) support this interpretation.