Turnout and the Calculation of Swing Ratios

A perennial topic of interest among legislative scholars is the relationship between votes won by parties in the electoral areana and seats won in the legislative arena. In studying this relationship scholars rely on a common concept--the swing ratio--with numerous operationalizations. The merits and demerits of various methods of calculating the swing ratio have been discussed before, but this paper deals with a consideration heretofore not given explicit attention--differential turnout across constituencies. The paper begins with a precise statement of the relationship the swing ratio is intended to measure, and proceeds to draw out the implications of differential turnout for regression measure of the swing ratio.