Reevaluating Two Measures of Inter-Party Competition in the American States

Abstract

Inter-party competition is an essential criterion for evaluating the quality of a democracy. American state politics scholars generally rely on two measures of competition: (1) Ranney’s (1965, 1976) measure of the partisan composition of state legislatures and governors’ offices and (2) Holbrook and Van Dunk’s (1993) measure of the competitiveness of state legislative elections. Previous research has incorporated the two measures inconsistently, with some studies using one measure as a substitute for the other and other studies using both measures in a single statistical model. At the heart of this confusion is a debate about whether the two indicators are measuring different dimensions of inter-party competition. We use data from state legislative partisan balance and election returns to compute the two measures of competition from 1970 to 2003. We show that while the two measures were positively correlated in the 1970s and 1980s, they are now negatively correlated. We explore a set of possible explanations for the recent divergence between the two measures and provide practical recommendations for researchers using a measure of inter-party competition in future studies.

Keywords: State politics, electoral competition