4 June 2010, Computational Social Choice Seminar, Burak Can
Collective decisions are modeled by preference correspondences. In particular we focus on a new conditioncalled "update proofness". It appears that although this condition seems to be very natural, it is satisfied by only a small number of preference correspondences. In fact, in case of consistent and pairwise correspondences the Kemeny-Young rule is singled out by this condition and in case of convex-valued images this condition implies that the correspondence equals the union of sets of preferences upon which any k agents unanimously agree, where k is related to the number of alternatives. In both cases it therewith provides a charaterization of these rules. This is joint work with Ton Storcken.