Collectively Rational Voting Rules for Simple Preferences
2010/03/09
研討會日期 : 2010-03-09
時間 : 14:30
主講人 : Professor Biung-Ghi Ju
地點 : B110
演講者簡介 : Professor Biung-Ghi Ju為Ph.D. in Economics，University of Rochester (2001)。現為韓國大學經濟系副教授。其主要研究領域為Economic Theory, Social Choice Theory, Public Economics, Game Theory, and Mechanism Design。
演講摘要 : Collective rationality of voting rules, requiring transitivity of social preferences (or quasi-transitivity, acyclicity for weaker notions), has been known to be incompatible with other standard conditions for voting rules when there is no prior information, thus no restriction, on individual preferences (Arrow, 1951; Sen, 1970). Inada (1964) proposes two restricted domains of individual preferences where majority voting generates transitive social preferences; they are the domain consisting of preferences that have at most two indifference classes, and the domain where any set of three alternatives is partitioned into two non-empty subsets and alternatives in one set are strictly preferred to alternatives in the other set. On these two domains, we investigate whether majority voting is the unique way of generating transitive, quasi-transitive, or acyclic social preferences. First of all, we rule out non-standard voting rules by imposing monotonicity, anonymity, and neutrality. Our main results show that majority rule is the unique voting rule satisfying transitivity, yet all other voting rules satisfy acyclicity (also quasi-transitivity on the second domain). Thus we find a very thin border dividing majority and other voting rules, namely, the gap between transitivity and acyclicity.
