Quality-adjusted Population Density

Quality-adjusted population density (QAPD) is population divided by l and 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.