Over a third of Africa’s 1 billion inhabitants currently live in urban areas, but by 2030 that proportion will have risen to a half. According to a recent report from UN-HABITAT, the United Nations agency for human settlements, the population of some cities is set to swell by up to 85% in the next 15 years. The most populous city in 2010, Cairo, will grow by 23% to 13.5m people. By 2025, however, it will have been overtaken by both Lagos (15.8m) and Kinshasa (15m). Food and water shortages, poor infrastructure and a lack of housing are among the problems faced by governments during such rapid urbanisation. Progress in meeting these challenges would be shown by a fall in the proportion of slum-dwellers, who currently account for 70% of urban inhabitants.