Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
I construct an index of political polarization using seven previously used measures. I estimate the relative propensity for polarization across demographic groups and examine the extent to which demographic change can explain recent trends in polarization. Assuming fixed propensities for polarization across groups, 34 percent of the change in polarization between 1984 and 2016 can be attributed to demographic change in the United States. Shifts in the educational, religious, and age compositions of the United States are the main contributing factors.