Between now and 2050, the urban population of Africa is likely to triple and that of Asia to increase by 61 per cent, so that by 2050 most of the world’s urban population will be concentrated in Asia (52 per cent) and Africa (21 per cent). In 1990, 10 urban agglomerations were characterized as “megacities”, with each hosting more than 10 million inhabitants. Together, they accounted for 7 per cent of the global urban population.