Where to draw the line: Data problems and other difficulties estimating urbanisation in Africa

The purpose of this article is to review the current state of knowledge on the pitfalls around definitions of the urban and the use of census data in estimating and tracking changes in urban populations. Differing criteria for the urban population and changing definitions make comparisons of levels of urbanisation very difficult across countries. Where censuses are held infrequently and administered less rigorously, accurate data on the urban population are a particular problem. This is especially the case in sub-Saharan Africa. Secondary African cities are increasingly important sites of urbanisation in sub-Saharan Africa, yet there is far less knowledge about these smaller cities. This article therefore looks at issues around estimates of populations in sub-Saharan cities and why this is a particular problem in smaller cities. Some of the implications of these problems are discussed, as well as measures to improve our understanding of the urbanisation process in smaller cities.