Identity Polarization and Social Change

Identity boundaries shape who connects with whom. I model how institutional shocks that polarize group identities—competing churches, partisan media, political movements—fragment social networks and create coordination barriers to behavioral change. To test this, I construct a linked dataset from 204 million Dutch vital records (1680–1920), introducing collective entity resolution methods to trace family networks and measure identity investment through naming patterns. As a first step, I show that the 1853 Catholic hierarchy restoration gradually increased religious segregation in marriage witness networks, with effects strongest in initially diverse communities.