Median voter theorem
When the options lie on a single line and each voter prefers whatever is nearest to them, two competing candidates are both pulled to the middle voter's position.
When the options lie on a single line and each voter prefers whatever is nearest to them, two competing candidates are both pulled to the middle voter's position.
Often misread asApplying it to multi-dimensional politics, or to races with three or more serious candidates, where the convergence result simply does not hold.
How to see it
On one dimension with two candidates, the middle voter decides
If every voter's view sits somewhere on a single line and each prefers outcomes nearer their own position, two candidates competing for votes both move towards the position of the median voter. Any candidate standing away from the middle can be beaten by one standing slightly closer to it. The result is convergence on the middle voter, which is not the same as representing the average voter.
The checkIt needs one dimension, single-peaked preferences and exactly two competitors. Relax any of those and candidates can have good reasons not to converge.
Try itFive voters sit at positions 1, 2, 3, 9 and 10. Work out the mean and the median. Then ask which position a candidate who only wants to win should take, and notice that they are not the same number.
Games that show it
Know these first
When it stops being true
- single-peaked-preferences
- binding-commitment-available
- two-contestant-field
Easily confused with
Sources
- Black, D. (1948). Journal of Political Economy 56(1), 23-34.
- Downs, A. (1957). Harper and Brothers, New York. Commonly cited as Harper & Row, which is the firm's post-1962 name.
- Hotelling, H. (1929). Economic Journal 39(153), 41-57.