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How much does a vote count? Voting power, coalitions, and the Electoral College

Gelman, Andrew and Katz, Jonathan N. (2001) How much does a vote count? Voting power, coalitions, and the Electoral College. Social Science Working Paper, 1121. California Institute of Technology , Pasadena, CA. (Unpublished)

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In an election, the probability that a single voter is decisive is affected by the electoral system—that is, the rule for aggregating votes into a single outcome. Under the assumption that all votes are equally likely (i.e., random voting), we prove that the average probability of a vote being decisive is maximized under a popular-vote (or simple majority) rule and is lower under any coalition system, such as the U.S. Electoral College system, no matter how complicated. Forming a coalition increases the decisive vote probability for the voters within a coalition, but the aggregate effect of coalitions is to decrease the average decisiveness of the population of voters. We then review results on voting power in an electoral college system. Under the random voting assumption, it is well known that the voters with the highest probability of decisiveness are those in large states. However, we show using empirical estimates of the closeness of historical U.S. Presidential elections that voters in small states have been advantaged because the random voting model overestimates the frequencies of close elections in the larger states. Finally, we estimate the average probability of decisiveness for all U.S. Presidential elections from 1960 to 2000 under three possible electoral systems: popular vote, electoral vote, and winner-take-all within Congressional districts. We find that the average probability of decisiveness is about the same under all three systems.

Item Type:Report or Paper (Working Paper)
Katz, Jonathan N.0000-0002-5287-3503
Additional Information:We thank Stephen Ansolabehere, Robert Erikson, and Amanda O'Brien for helpful comments.
Group:Social Science Working Papers
Subject Keywords:coalition, decisive vote, electoral college, popular vote, voting power
Series Name:Social Science Working Paper
Issue or Number:1121
Record Number:CaltechAUTHORS:20170807-140415393
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79857
Deposited By: Jacquelyn Bussone
Deposited On:07 Aug 2017 22:12
Last Modified:19 Nov 2020 18:28

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