We characterize all preference profiles at which the approval (voting) rule is manipulable, under three extensions of preferences to sets of alternatives: by comparison of worstalternatives, best alternatives, or by comparison based on stochastic dominance. We perform a similar exercise for...

Single-plateaued preferences generalize single-peaked preferences by allowing for multiple bestelements. These preferences have played an important role in areas such as voting,strategy-proofness andmatching problems. We examine the notion of single-plateauedness in a choice-theoretic...

We consider voting rules on a multidimensional policy space for a continuum of voters with elliptic preferences. Assuming continuity, y-strategy-proofness - meaning that coalitions of size smaller or equal to a small number y cannot manipulate - and unanimity, we show that such rules are...

Following prospect theory we consider decision making under risk in which the decision maker''s preferences depend on a reference outcome. An outcome below this reference outcome is regarded as resulting from a loss: a loss decreases the decision maker''s basic utility more than a comparable...

Under a k-approval scoring rule each agent attaches a score of one to his k most preferred alternatives and zero to the other alternatives. The rule assigns the set of alternatives with maximal score. Agents may extend preferences to sets in several ways: they may compare the worst alternatives,...

The Rubinstein alternating offers bargaining game is reconsidered under the assumption that each player is loss averse and the associated reference point is equal to the highest turned down offer of the opponent in the past. This makes the payoffs and therefore potential equilibrium strategies...

Voting problems with a continuum of voters and finitely many alternatives are considered. The classical Arrow and Gibbard-Satterthwaite theorems are shown to persist in this model, not for single voters but for coalitions of positive size. The emphasis of the study is on strategic...

Effectivity functions for finitely many players and alternatives are considered. It is shown that every monotonic and superadditive effectivity function can be augmented with equalchance lotteries to a finite lottery model---i.e., an effectivity function that preserves the original effectivity...

We analyse the problem of aggregating judgments over multiple issues from the perspective ofefficient aggregation of voters’ private information. While new in judgment aggregation theory,this perspective is familiar in a different body of literature about voting between twoalternatives when...

A state, for instance a health state, is characterized by a number of attributes to each of which a level is assigned. A specific collection of numerical values, for instance utilities, for all possible states is called a situation. The main purpose of the paper is to develop a class of methods...