, Volume 47, Issue 3, pp 1687-1701
Date: 07 Oct 2011

How similar are they? rethinking electoral congruence

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Electoral continuity and discontinuity have been a staple of voting research for decades. Most researchers have employed Pearson’s r as a measure of congruence between two electoral outcomes across a set of geographic units. This paper argues that that practice should be abandoned. The correlation coefficient is a measure of linearity, not similarity, and is almost always the wrong measure. The paper recommends other quantities that better accord with what researchers usually mean by electoral persistence. Replications of prior studies in American and comparative politics demonstrate that the consequences of using r when it is inappropriate can be stark. In some cases what we think are continuities are actually discontinuities.

Earlier versions of this paper were presented at seminars at UC Berkeley, BYU, and Stanford University, as well as at the 2008 annual meetings of the Southwestern and Midwest Political Science associations and the Society for Political Methodology.