Measuring Public Opinion: The Wasserstein Bipolarization Index

Thomas M. Menino Convention & Exhibition Center 

The extent to which the American public is politically polarized is of great interest in the lay and academic communities. To study opinion polarization, political scientists and public opinion researchers examine the distribution of respondents on survey items, using visual comparison of histograms and/or measures such as variances and bimodality coefficients. We prove these measures fail to align with prevailing conceptualizations of polarization put forth in the literature. To remedy this situation we specify several properties a measure of polarization consistent with these conceptualizations should possess: in particular, it should increase as a distribution spreads away from a center toward the poles and/or as clustering below or above this center increases. We then propose a p-Wasserstein bipolarization index that satisfies these properties and measures the distance between the distribution of an item and a most polarized distribution with all mass concentrated on the lower and upper endpoints of the scale, using the index to examine bipolarization in attitudes toward governmental COVID-19 vaccine mandates across 11 countries.

Polarization

Wasserstein Distance

Public Opinion

COVID-19 Vaccination Mandates

Political Methodology 

Social Statistics Section