Rational aggregation rules

Abstract

This paper deals with the aggregation of individual fuzzy preference relations. The idea behind a democratic fuzzy aggregation rule is in the first place related to the concepts of individual power and social consensus, and it is pointed out that the translation into this context of Arrow's Theorem should be made not only requiring some appropriate ethical conditions, but also making reference to some kind of underlying rationality. Due to the existence in practice of intermediate states between extreme rationality and extreme irrationality, a fuzzy treatment of irrationality may appear sometimes to be more realistic than a crisp concept of pure rationality. In this paper, a particular measure for the degree of rationality of fuzzy preferences is assumed in a basic Arrow-like model, and a sufficient condition for non absolutely irrational (N.A.I.) aggregation rules is obtained.