Quality-adjusted Population Density
Quality-adjusted population density (QAPD) is population divided by land area that has been adjusted for geographic characteristics. We derive weights on these geographic characteristics from a global regression of population density at the quarter-degree level with country fixed effects. We show, first, that while income per capita is uncorrelated with conventionally measured population density across countries, there is a strong negative correlation between income per capita and QAPD; second, that the magnitude of this relationship exceeds the plausible structural effect of density on income, suggesting a negative correlation between QAPD and productivity or factor accumulation; and third, that higher QAPD in poor countries is primarily due to population growth since 1820. We argue that these facts are best understood as results of the differential timings of economic takeoff and demographic transition across countries, and particularly the rapid transfer of health technologies from early to late developers.
We are grateful to Anna Croley, Joao Garcia, Bo Yeon Jang, and Balazs Zelity for excellent research assistance; to Jesus Fernandez Villaverde, Matthew Delventhal, Gajendran Raveendranathan, and Ömer Özak for sharing data; to seminar audiences at Clark University, Louisiana State University, Southern Methodist University, the University of Southern Denmark, The Max Planck Institute for Demographic Research, the Second Workshop on Geodata in Economics (Hamburg, 2019), the Federal Reserve Bank of New York, University of Haifa, Hebrew University, and IDC Herzliya for helpful comments; and to Andrew Foster and Joshua Wilde for helpful advice. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research.