Median voter theory

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The parties A and B want to catch the median voters and they will walk to the centre. The red and blue areas represent the voters already won.^{[dubious — see talk page]}

Median voter theory, also known as the median voter theorem and the median voter model, is a famous voting model positing that in a majority election, if voter policy preferences can be represented along one dimension (i.e., if every voter's political ideology can be pinpointed on a line), if a voter always votes for the politician that commits to a policy position closest to their own preference, and if there are only two politicians, then if the politicians want to maximize their number of votes (and are prepared to choose policies purely to achieve this) they should both commit to the policy position preferred by the median voter. This politician strategy is the Nash equilibrium of the game (see game theory). It results in both politicians receiving half the votes, and if either candidate deviates to commit to a different policy position, the deviating candidate receives less than half the vote. simple example

Roger Congleton further identifies two versions of the median voter theorem: a weak form which says that the median voter "casts his or her vote for the policy that is adopted," and a strong form, which states that the median voter "always gets her most preferred policy." (Congleton, 2002).

If a poll shows that a candidate is behind, that candidate may respond by attempting to become more like the opposition in order to gain more votes from the opponent's side of the spectrum.

[edit] History of median voter theory

The theorem was first articulated in Duncan Black's 1948 article, "On the Rationale of Group Decision-making" and popularized by Anthony Downs's 1957 book, An Economic Theory of Democracy. Earlier thinkers such as Condorcet and Harold Hotelling hinted at similar formulations (although Hotelling's model in his paper Stability in Competition had a huge mathematical mistake, its main idea — that politicians would compete to be the most middle of the road — was adopted as other models with the same thesis were invented) but did not receive widespread recognition for the identification of this simple idea that is nonetheless easily observed in modern elections. (Congleton, 2002).

[edit] Applied

[edit] References

Black, Duncan (1948). "On the Rationale of Group Decision-making". Journal of Political Economy 56: 23-34.
Downs, Anthony (1957). An Economic Theory of Democracy. Harper Collins.
Congleton, Roger (2002). The Median Voter Model. In * C. K. Rowley (Ed.); F. Schneider (Ed.) (2003). The Encyclopedia of Public Choice. Kluwer Academic Press.