The structure of two-valued strategy-proof social choice functions with indifference

Document pages: 26 pages

Abstract: We give a structure theorem for all coalitionally strategy-proof socialchoice functions whose range is a subset of cardinality two of a given largerset of alternatives.We provide this in the case where the voters agents are allowed to expressindifference and the domain consists of profiles of preferences over a societyof arbitrary cardinality. The theorem, that takes the form of a representationformula, can be used to construct all functions under consideration.