The authors of Africapolis (2008) detected in this the beginning of the urbanisation process, in which countries in the region have reached different stages: one of initial urbanisation based at the outset on a small number of settlements, then the appearance and development of secondary towns until the urban network is large enough for the pool of rural migration to start dwindling. Finally, when the demographic transition is accomplished, the number of urban centres and the urban population level out, with some centres losing ground to others. These phenomena are a means of understanding the potential linkages and scope for movement and trade between places.