Cities in Sub-Saharan Africa are experiencing rapid population growth. Yet their economic growth has not kept pace. Why? One factor might be low capital investment, due in part to Africa's relative poverty: Other regions have reached similar stages of urbanization at higher per capita GDP. This study, however, identifies a deeper reason: African cities are closed to the world. Compared with other developing cities, cities in Africa produce few goods and services for trade on regional and international markets To grow economically as they are growing in size, Africa's cities must open their...