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Wednesday, August 05, 2020
12:00 PM - 1:00 PM
Online Event

Ulric B. and Evelyn L. Bray Social Sciences Seminar

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.