The fast and often chaotic urbanization of the developing world generates both economic opportunity and challenges, like contagious disease and congestion, because proximity increases both positive and negative externalities. In this paper, we review the expanding body of economic research on...

In 1956, 52% of urban men and 42% of rural men smoked cigarettes. By 2010, the disparity had flipped: 24.7% of urban men and 30.6% of rural men smoked. Smoking remains the greatest preventable cause of mortality in the United States, and understanding the underlying causes of place-specific...

The economic approach to cities relies on a spatial equilibrium for workers, employers and builders. The worker's equilibrium implies that positive attributes in one location, like access to downtown or high wages, are offset by negative attributes, like high housing prices. The employer's...

Africa is urbanizing rapidly, and this creates both opportunities and challenges. Labor productivity appears to be much higher in developing-world cities than in rural areas, and historically urbanization is strongly correlated with economic growth. Education seems to be a strong complement to...

A key reason for the existence of cities are the externalities created when people cluster together in close proximity. During Covid, such interactions came with health risks and people found other ways to interact. We document how cities changed during Covid and consider how the persistence of...