Median Voter Theorem
Carol Xiang at Edgeworth Economics (reference below) describes the median voter theorem as the proposition “that a majority voting mechanism will select the outcome that is preferred by the median voter.”
Originated in Harold Hotelling’s discussions about how political candidates’ platforms tend to converge during majoritarian elections, the Median Voter Theorem was formalized by Duncan Black in his work on majority voting and Anthony Downs in his research on representative democracy …. [T]he Median Voter Theorem is a simplified model of the majority voting system. There are some crucial assumptions that can possibly make the theory fail to explain election results. For example, the assumption that voters can easily place themselves and the candidates on a single-dimensional political spectrum is fundamental to the model. In reality, voters may be liberal on issues related to individual rights but conservative on some economic policies; candidates may also have different ideologies for different issues.
“Additionally, the model assumes that there are only two main candidates running for office, which was not the case for the presidential election of 2000 (Bush, Gore and Nader). When a third party comes into the race, the center may no longer be the equilibrium point because it matters where each candidate stands on the ideology spectrum. For example, Gary Johnson from the Libertarian Party may capture some voters who would otherwise have voted for either Hillary Clinton or Donald Trump had he not run in this election.
“Another question we need to keep in mind is whether the outcome preferred by median voters is necessarily the most efficient or not. When the distribution of voters is skewed on the political continuum, median voters’ preferred polices may not maximize social benefits. Finally, it is important to note that in the United States the President is elected by the Electoral College, not by a majority. Nevertheless, the model can be useful in explaining political behavior.
“Even with those assumptions that are not necessarily met in reality, we can still see some traces of the theory in terms of how candidates tend to shift their positions after primary elections.”
Tyler Cowen and Alex Tabarrok, through Marginal Revolution University, have created an excellent 8-minute video on the Theory of the Median Voter, available at https://www.youtube.com/watch?v=Z929jakmH8w, accessed 22 May 2018. This video highlights some of the pros and cons of different voting systems, including first-past-the-post and proportional representation.
Carol Xiang (2016), How Game Theory Helps Explain Politics: The Median Voter Theorem, at https://edgewortheconomics.com/experience-and-news/edgewords-blogs/edgewords/article:game-theory-explains-politics-median-voter-theorem/, accessed 22 May 2018.
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Page created by: Alec Wreford and Ian Clark, last modified 22 May 2018.
Image: Tyler Cowen and Alex Tabarrok, Theory of the Median Voter, Marginal Revolution University, at https://www.youtube.com/watch?v=Z929jakmH8w, accessed 22 May 2018.