Although urbanism in terms of “a relatively large, dense, and permanent settlement of socially heterogeneous individuals” is not a general characteristic of traditional life, it is far from being unique in West Africa. In 1911 there were already twenty-nine towns of over 3,000 inhabitants in what is now southern Ghana, and this degree of urban concentration is small compared with western Nigeria. The Yoruba of that region have six cities of more than 100,000, including Ibadan, which is the largest Negro city in Africa. In 1931 some 28 per cent of the Yoruba lived in nine cities of 45,000 inhabitants, while 34 per cent of the population lived in sixteen cities of over 20,000 inhabitants. In addition, there were twenty-seven centers with populations between 10,000 and 19,999. Bascom has calculated that the estimated index of urbanization of Yoruba cities falls between that of the United States and Canada and that the distribution of population in urban centers is very similar to that of France.