Over 800 million people in Africa, Asia, and Latin America live in slums. Why? I argue that slums are a result of ‘‘disjointed modernization” and show that 70% of cross-country variation in slum incidence is explained by demographic, economic, and institutional factors. I trace the origins of disjointed modernization in sub-Saharan Africa back to the colonial period and show that colonial era investments and institutions are reflected in contemporary variation in slum incidence. I argue that status quo interests and the rise of an anti-urbanization bias in development discourse have inhibited investment and reform in the postcolonial era.

According to UN-Habitat. (2008) over 800 million people in Africa, Asia, and Latin America live in slums i.e., urban areas characterized by some combination of tenuous dwelling structures, overcrowding, and lack of access to adequate water and sanitation facilities. Improving the lives of slum dwellers is one of the most pressing development challenges of the 21st century. United Nations projections suggest that all of the world’s population growth in the next 50 years will be absorbed by towns and cities in developing regions and World Bank research has shown that urban poverty is growing even as rural poverty has begun to decline (Ravallion, Chen, & Sangraula, 2007; United Nations., 2012). Despite these trends, surprisingly little systematic comparative research has been devoted to understanding the dynamics of urban poverty and development in recent decades. The ‘‘challenge of slums” is particularly acute in sub-Saharan Africa. Although the region contains just 13% of the urban population of developing regions it hosts 25% of the slum population of developing regions (UN-Habitat, 2008). Over 60% of sub-Saharan Africa’s urban population lives in slum conditions; the highest level of ‘‘slum incidence” of any major world region and significantly higher than the developing region average of 32.7% (UN-Habitat, 2008). However, conditions in urban areas vary considerably across countries within the region.