A Theory of Partisan Sorting and Geographic Polarization

 I propose a mechanism for partisan sorting and geographic polarization which is tested using the mass migration of African-Americans from New Orleans to Houston, Texas in the aftermath of Hurricane Katrina. According to the Migration-Polarization (MP) Theory, diversity-increasing migration events induce flight (migration) among ideological conservatives. These changes, in turn, produce geographically polarized spaces along partisan lines. Using an exogenous shock to African-American student enrollment in Houston schools as the result of Hurricane Katrina, evacuee data from apartment buildings in Harris Country and a variety of empirical tools including synthetic controls, I demonstrate that African-American Katrina migration led to Republican flight, declines in housing values and geographic polarization.