Centrist bias

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Centrist bias is a political spectrum statistic that measures the tendency for elected candidates to be near the mean voter.

Definition[edit | edit source]

The centrist bias of a set of winning candidates with respect to a given political spectrum is equal to Pearson's correlation coefficient between the distance of a voter from the mean voter and the distance of that voter from the nearest winning candidate.

Example[edit | edit source]

Assume a one-dimensional political spectrum with the voter distribution

  • 15% at position 0
  • 20% at position 0.25
  • 30% at position 0.5
  • 20% at position 0.75
  • 15% at position 1

If the candidate set {0.25, 0.75} is elected, then

voters position distance from mean nearest winner distance from winner
15% 0.00 0.50 0.25 0.25
20% 0.25 0.25 0.25 0.00
30% 0.50 0.00 either 0.25
20% 0.75 0.25 0.75 0.00
15% 1.00 0.50 0.75 0.25

To compute the centrist bias, we consider the (distance from mean, distance from winner) pairs:

  • (0.50, 0.25) with frequency 30%
  • (0.25, 0.00) with frequency 40%
  • (0.00, 0.25) with frequency 30%

The correlation, and thus the centrist bias, is zero.