My explanation of the observed association is based on the Structural-Demographic Theory: (1) labor oversupply (proxied by immigration) leads to (2) elite overproduction (proxied by wealth inequality) and heightened intraelite competition that, in turn, results in (3) elite fragmentation (proxied by political polarization). Note that this explanation was not constructed post hoc, after observing the empirical associations between polarization, inequality, and immigration. Instead, each of these variables serves as a proxy for the movements of the structural forces postulated by the theory.
