When an agent decides whether to join a coalition or not, she must consider both i) the expected strength of the coalition and ii) her position in the vertical structure within the coalition. We establish that there exists a positive relationship between the degree of inequality in remuneration across ranks within coalitions and the number of coalitions to be formed. When coalition size is unre...

We consider the problem of a society whose members must choose from a …nite set of alternatives. After knowing the chosen alternative, members may reconsider their membership by either staying or exiting. In turn, and as a consequence of the exit of some of its members, other members might now …nd undesirable to belong to the society as well. For general exit procedures we analyze the exit beha...

We consider the problem of how societies should be partitioned into classes if individuals express their views about who should be put with whom in the same class. A non-bossy social aggregator depends only on those cells of the individual partitions the society members classify themselves in. This fact allows us to concentrate on a corresponding “opinion graph” for each pro…le of views. By mea...

The purpose of this paper is to examine the impact of a community’s economic characteristics on its ability to generate adherence to socially efficient norms. These norms prescribe a behavior for an individual when his/her preferred behavior imposes a negative externality on others. This paper explores social norms as a mechanism of how neighborhood characteristics can affect individual behavio...

Why is there such wide-spread opposition to immigration, although attitudes are generally favorable towards trade? Using concepts from population ethics, this paper shows that impartial observers oppose unskilled immigration if they are inequality-averse, base their decisions on national interest, and have an integrative view of immigration. Moreover, unskilled immigration makes redistribution ...

We consider the problem of allotting shares of a task or good among agents with single peaked preferences over their own shares. Previous characterizations have examined rules, such as the uniform rule, which satisfy various symmetry requirements. We consider the case where agents might begin with natural claims to minimal or maximal allotments, or might be treated with different priorities. We...

A general model of aggregation of binary evaluations over interrelated issues, introduced by Wilson and further studied by Rubinstein and Fishburn and by the authors, is extended here to allow for abstentions on some of the issues. It is shown that the same structural conditions on the set of feasible evaluations that lead to dictatorship in the model without abstentions, lead to oligarchy in t...

Arrow’s impossibility theorem states that if a collective choice rule satisfies unrestricted domain, weak Pareto, independence of irrelevant alternatives, and collective rationality, then there exists a dictator. Among others, Arrow’s postulate of collective rationality is controversial. We propose a new axiom for a collective choice rule, decisiveness coherence, which is weaker than collective...

The Nakamura number of a simple game plays a critical role in preference aggregation (or multi-criterion ranking): the number of alternatives that the players can always deal with rationally is less than this number. We comprehensively study the restrictions that various properties for a simple game impose on its Nakamura number. We find that a computable game has a finite Nakamura number great...

This paper considers social choice theory without the Pareto principle. We revisit the trade-off theorem developed by Campbell and Kelly (Econometrica 61:1355– 1365, 1993), and generalize their result. By introducing an alternative criterion of power structure, a dominance relation, we show that if a social welfare function on the unrestricted domain satisfies the independence of irrelevant alt...