Comparing city size distributions: Gridded population versus nighttime lights

Abstract

This paper compares the size distributions of cities when they are measured using gridded population and nighttime lights (NTLs) data. To do so, we exploit recent and accurate satellite imagery to proxy urban economic activity. Similarly to related studies, our results suggest that population is more equally distributed than lights at the country level. However, and calling assumptions established for urban NTLs into question, our findings do not support a Pareto function for their distribution. We also obtain evidence of a nonlinear and heterogeneous link between population and lights for a global sample of cities. Grounded on our empirical analysis, we develop a simple theoretical framework that relates the difference between the distributions of population and light emissions to the strength of agglomeration economies.