The Urban Mortality Transition and Poor-Country Urbanization

Today the world's fastest-growing cities lie in low-income countries, unlike the historical norm. Also unlike the "killer cities" of history, cities in low-income countries grow not just through in-migration but also through their own natural increase. First, we use novel historical data to document that many poor countries urbanized at the same time as the postwar urban mortality transition. Second, we develop a framework incorporating location choice with heterogeneity in demographics and congestion costs across locations to account for this. In the framework, people prefer to live in low-mortality locations, and the aggregate rate of population growth and the locational choice of individuals interact. Third, we calibrate this to data from a sample of poor countries, and find that informal urban areas (e.g. slums) can absorb additional population more easily than other locations. We show that between 1950 and 2005 the urban mortality transition could have doubled the urbanization rate as well as the size of informal urban areas in this sample. Of these effects, one-third could be attributed to the amenity effect of lower urban mortality rates, while the remainder is due to higher population growth disproportionately pushing people into informal urban areas. Fourth, simulations suggest that family planning programs, as well as industrialization or urban infrastructure and institutions may be effective in slowing poor-country urbanization.