Factoring out the impossibility of logical aggregation


Journal of Economic Theory

juillet 2008, vol. 141, n°1, pp.100-113

Départements : Economie et Sciences de la décision, GREGHEC (CNRS)

According to a theorem recently proved in the theory of logical aggregation, any nonconstant social judgment function that satisfies independence of irrelevant alternatives (IIA) is dictatorial. We show that the strong and not very plausible IIA condition can be replaced with a minimal independence assumption plus a Pareto-like condition. This new version of the impossibility theorem likens it to Arrow's and arguably enhances its paradoxical value. Keywords: Discursive dilemma; Doctrinal paradox; Impossibility theorems