An Anatomy of Urbanization in Sub-Saharan Africa

This Sciences Po Economics Discussion Paper was also part of a set of two Policy Research Working Papers that have been produced under the World Bank’s “A Move to Consistency – Integrating the Consistent Measurement of Urbanization into Global Poverty Measurement” Advisory Services and Analytics project (P175622). This paper was published as Policy Research Working Paper No. WPS10621. The accompanying paper – entitled “Where is Poverty Concentrated? New Evidence Based on Internationally Consistent Urban and Poverty Measurements” – is available as Sciences Po Economics Discussion Paper 2023-05 (WB Policy Research Working Paper No. WPS10620). This paper provides a detailed descriptive analysis of patterns of urbanization across Sub-Saharan Africa for the year circa 2015. Despite the rapidity and importance of Sub-Saharan Africa’s urbanization, little is known about the anatomy of patterns of urbanization across the region due to a lack of detailed and accurate official data on urban settlements and populations. To address this gap, the paper applies a modified version of the “dartboard” algorithm to high-resolution gridded population data for the region, which is derived from digitized maps of the footprints of all buildings in the region from very high-resolution satellite imagery. This allows for a consistent definition of urban areas across all countries in the region, overcoming the measurement problems that arise from relying on official definitions of urban areas, which vary markedly across countries. Using this definition, the paper presents evidence on key empirical regularities that are related to disparities across the urban hierarchies, such as the extent of urban primacy and Zipf’s law, as well as on the internal structures of cities, such as population density gradients and the number of centers that cities possess. The paper also analyzes how these characteristics are related to key country characteristics. Finally, the paper compares the results with those that arise from the use of an alternative definition of urban areas—the degree of urbanization.