Subnational administrative units are fundamental to territorial states and their political topography, but we lack theory and evidence on how their borders are designed. I argue that aligning administrative borders with ethnic geography and creating homogeneous, “packed” units facilitates local institutional persistence and increases short term governance efficiency. Yet, centralizing governments may instead design heterogeneous units and “crack” groups, thus subverting their institutions. I test this argument by studying unit-design in Sub-Sahara Africa. I contrast indirect with more direct colonial rule and use new data on administrative and early-colonial ethnic geography derived from historical maps. Modeling subnational borders with a probabilistic spatial partition model, I find strong positive associations with ethnic boundaries. These effects are stronger under indirect British compared to more direct French rule which engaged in more cracking. The papers’ novel theory, data, and methods advance our understanding of the varying ethno-geographic roots of administrative geographies in Africa.

Carl Müller-Crepon's research focuses on state building and its effects on local development and conflict, in particular in Africa. His most recent work explores the reciprocal relationship between ethnic geographies and (sub-)national political borders in Africa and Europe since the 19th century. Until August 2022, Carl was a Lecturer at the Department of Politics and International Relations at the University of Oxford. Previously, he was a PostDoc at the International Conflict Research Group at ETH Zurich and a visiting scholar at Harvard University’s Institute for Quantitative Social Science. Throughout, Carl innovates and uses computational methods to collect and analyse large, mostly geospatial datasets. His work has been published in International Organization, the British Journal of Political Science, the Journal of Peace Research, the Journal of Conflict Resolution, and Political Science Research and Methods.