Map showing the 20 cities projected to have the fastest growth rate (2020-2025) in the world. Top of the list is Gwagwalada, Nigeria (6.46% projected growth). All of the top 20 cities are from Asia or Africa. The main factor for such rapid growth is the high birth rate and a drastic shift in populations migrating from the countryside to the cities. Data from UN World Urbanization Prospects 2018.