Acemoglu and Johnson (2007) present evidence that improvements in population health do not promote economic growth. We show that their result depends critically on the assumption that initial health has no causal effect on subsequent economic growth. We argue that such an effect is likely,...

This paper examines data on urbanization. We review the most commonly used data sources, and highlight the difficulties inherent in defining and measuring the size of urban versus rural populations. We show that differences in the measurement of urban populations across countries and over time...