By 2050, 70 per cent of the world’s population is projected to live in urban areas. Rapid urban growth is mainly occurring in countries least able to cope with the demand for decent jobs, adequate housing and urban basic services. Close to one billion people, or 33 per cent of the urban population in developing countries, live in slums, in inequitable and often life-threatening conditions. If left unaddressed, these trends may become sources of social and political instability."
Urbanization, Cities and Sustainable Development