Acyclic social choice from finite sets

This paper characterizes acyclic preference aggregation rules under various combinations of monotonicity, neutrality, decisiveness, and anonymity, in the spirit of Nakamura's (1979) Theorem on the core of simple games. Each of these characterizations can be seen to follow from Ferejohn and Fishburn's (1979) result on acyclic aggregation rules assuming only independence of irrelevant alternatives. We then state as corollaries to these characterizations extant results such as Sen's (1970) liberal paradox, Blau and Deb's (1977) theorem on the existence of vetoers, and Brown's (1975) theorem on the non-emptiness of the collegium.I thank David Austen-Smith, Michel Le Breton, Maurice Salles, and two anonymous referees for numerous enlightening conversations and comments. I also thank the National Science Foundation and Sloan Foundation for generous financial assistance.