$$※ v_i: 得票率, s_i: 議席率$$

Rae’s Index (Rae 1967)

$$I = \frac{1}{n}\sum_i^n|v_i – s_i|$$

Loosemore-Hanby’s Index (Loosemore and Hanby 1971)

$$D = \frac{1}{2}\sum_i^n |v_i – s_i|$$

Least Square Index (Gallagher 1991)

$$LSq = \sqrt{\frac{1}{2}\sum(v_i – s_i)^2}$$

Lijphart index (Lijphart 1994)

$$max|v_i – s_i|$$

Saint-Lague index

$$\sum\frac{1}{v_i}(s_i – v_i)^2$$

D’Hont index (Taagepera and Laakso 1980)

$$max\Bigl{(}\frac{s_i}{v_i}\Bigr{)}$$

Regression index(Cox and Shugart 1991)

$$b = \frac{\sum x_i y_i}{\sum x^2_i}$$
$$※ x_i = v_i; y_i = s_i$$