Building tribes: How administrative units shaped ethnic groups in Africa

Ethnic identities around the world are deeply intertwined with modern statehood, yet the extent to which territorial governance has shaped ethnic groups is empirically unknown. I argue that governments at the national and subnational levels have incentives to bias governance in favor of large groups. The resulting disadvantages for ethnic minorities motivate their assimilation and emigration. Both gradually align ethnic groups with administrative borders. I examine the result of this process at subnational administrative borders across sub‐Saharan Africa and use credibly exogenous, straight borders for causal identification. I find substantive increases in the local population share of administrative units' predominant ethnic group at units' borders. Powerful traditional authorities and size advantages of predominant groups increase this effect. Data on minority assimilation and migration show that both drive the shaping of ethnic groups along administrative borders. These results highlight important effects of the territorial organization of modern governance on ethnic groups.