A New Measure of Congruence: The Earth Mover's Distance. (22nd February 2017)

• Record Type: Journal Article
• Authors: Lupu, Noam; Selios, Lucía; Warner, Zach
• Is Part Of: Political analysis. Volume 25:Number 1(2017)
• Page Start: 95
• Page End: 113
• Publication Date: 2017-02-22
• Subjects: Political science -- Methodology -- Periodicals; Electronic journals; 320.011
• DOI: 10.1017/pan.2017.2
• Languages: English
• ISSNs: 1047-1987

Abstract

Abstract : Scholars of representation are increasingly interested in mass–elite congruence—the degree to which the preferences of elected elites mirror those of voters. Yet existing measures of congruence can be misleading because they ignore information in the data, require arbitrary decisions about quantization, and limit researchers to comparing masses and elites on a single dimension. We introduce a new measure of congruence—borrowed from computer science—that addresses all of these problems: the Earth Mover's Distance (EMD). We demonstrate its conceptual advantages and apply it to two debates in research on mass–elite congruence: ideological congruence in majoritarian and proportional systems and the determinants of congruence across countries in Latin America. We find that improving measurement using the EMD has important implications for inferences regarding both empirical debates. Even beyond studies of congruence, the EMD is a useful and reliable way for political scientists to compare distributions.