Population Dynamics, Urbanisation without Growth, and the Rise of Megacities

That urbanisation in many developing countries, especially in Sub-Saharan Africa, is not delivering the kind of benefits that might be expected in the light of experience elsewhere in the world is now widely acknowledged. This urbanisation without growth has been the focus of recent research in both the development and urban economics literature. In this paper, we focus on demographic factors and develop a simple dynamic model to describe internal migrations, the evolution of the urban rate and total productivity, and how these are affected by population growth and investments in urban infrastructure. Our model can predict basic trends in the data, including urbanisation without growth and the rise of (poor) megacities. We complement the model with empirical evidence using (i) international cross-country panel data; and (ii) regional data from Tanzania.