The Effects of Urban Diversity on Geographic Polarization: Evidence from Hurricane Katrina Migration

Abstract

Recent research suggests that suburbanization precipitated by the development of the Interstate Highway System drew Republican residents out of urban centers and gave rise to geographic political polarization between cities and suburbs (Nall 2015). In recent years, however, the rate of geographic political polarization has more than doubled while suburban growth declined and Interstate Highway construction ceased. In this paper, we argue that these recent trends can be explained by a complimentary push migration mechanism of demographic change facilitated by existing infrastructure in which increases to urban racial and ethnic diversity catalyze the out-migration of Republican leaning residents. Using a rapid, exogenous increase to Houston's African-American population as the result of Hurricane Katrina, we show that this mechanism can account for more recent increases in geographic polarization in the absence of concurrent changes to urban or suburban infrastructure.