Ulric B. and Evelyn L. Bray Social Sciences Seminar

Wednesday, August 5, 2020
12:00pm to 1:00pm
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Online Event
Arrow's Theorem, May's Axioms, and the Borda Count
Eric S. Maskin, Adams University Professor and Professor of Economics and Mathematics, Harvard University,

Abstract: We argue that Arrow's (1951) independence of irrelevant alternatives condition (IIA) is unjustifiably stringent. Although, in elections, it has the desirable effect of ruling out spoilers (Candidate A spoils the election for B if B beats C when all voters rank A low, but C beats B when some voters rank A high - - A "siphons" off support from B), it is stronger than necessary for this purpose. Worse, it makes a voting rule insensitive to voters' preference intensities. Accordingly, we propose a modified version of IIA to address these problems. Rather than obtaining an impossibility result, we show that a voting rule satisfies modified IIA, Arrow's other conditions, and May's (1952) axioms for majority rule if and only if it is the Borda count (Borda 1781), i.e., rank-order voting.

How to view the seminar:
Sign up for a free twitch.tv account, and tune in on Wednesdays at noon pacific time on twitch.tv/caltechecontheory. You will be able to ask questions on the twitch chat.

For more information, please contact Letty Diaz by phone at 626-395-1255 or by email at letty.diaz@caltech.edu.