Political Analysis Advance Access originally published online on April 3, 2009
Political Analysis 2009 17(2):162-176; doi:10.1093/pan/mpp003
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The Microfoundations of Mass Polarization
Department of Political Science, University of Pennsylvania, 208 South 37th Street, Philadelphia, PA 19104 e-mail: mleven{at}sas.upenn.edu (corresponding author)
Although there has been considerable attention to the question of how much polarization there is in the mass electorate, there has been much less attention paid to the mechanism that causes polarization. I provide evidence demonstrating the occurrence of individual-level conversion—individual Democrats and Republicans becoming more liberal and conservative. Although over the short term most of the observed changes are quite small and cannot be distinguished from measurement error, over time and many respondents, these movements aggregate to generate polarization. Small individual-level preference shifts provide an important foundation for aggregate polarization.
Authors’ note: Thanks to Sarah Anderson, Julia Azari, Daniel Bergan, David Brady, John Bullock, Daniel Butler, Hahrie Han, Sunshine Hillygus, Greg Huber, Bill Jacoby, John Lapinski, Laura Miller, Neil Malhotra, Jeremy Pope, Shawn Treier, the anonymous referees, and especially Simon Jackman for helpful comments. Any remaining errors are my own. The online appendix is available on the Political Analysis Web site.