This paper is concerned with preference-aggregation rules satisfying desirable efficiency and solidarity requirements. We formulate weaker versions of existing solidarity axioms and show how they imply, in conjunction with strategy-proofness, the existence of reference outcomes holding...

Fuzzy set theory has been explicitly introduced to deal with vagueness and ambiguity. One can also use probability theory or techniques borrowed from philosophical logic. In this chapter, we consider fuzzy preferences and we survey the literature on aggregation of fuzzy preferences. We restrict...

We propose a democratic preference aggregation function using trapezoidal fuzzy numbers. Examples are constructed to illustrate the proposed technique to optimize the problem by avoiding paradoxical outcomes without the fear of indecision

Politicians, CEOs and various other types of dictators make social choices that influence both their own and others' welfare. When a dictator's preferred alternative differs from recipients', it is unclear which preferences they aggregate and how they determine this set of admissible...

Consider a setting in which individual strict preferences need to be aggregated into a social strict preference relation. For two alternatives and an odd number of agents, it follows from May’s Theorem that the majority aggregation rule is the only one satisfying anonymity, neutrality, and...

We know that a strategyproof mechanism does not exist that is ordinally efficient and fair in the sense of equal division lower bound. We show that this impossibility for random assignments prevails even if agents have uniform preferences where a weakly decreasing utility function determines...

We present simple and direct arguments to characterize strongly group strategy-proof social choice functions whose range is of cardinality two. The underlying society is of arbitrary cardinality, and agents can be indifferent among alternatives.