Perpetual Motion: Human Mobility and Spatial Frictions in Three African Countries

Frictions affecting human mobility have been identified as important potential sources of the spatial gaps in wages and living standards that characterize many low-income coun¬tries. However, little direct data has been available to characterize mobility. Many surveys and censuses provide only limited information and focus on longer-term migration deci¬sions. In this paper, we use a novel data source that provides highly detailed location data on more than one million devices across three large African countries for an entire year. This allows us to examine high-frequency mobility patterns for a subset of high-quality observations for whom we can determine home locations confidently. We link our users with spatial data on population density and nationally representative micro-survey data to characterize this non-random sample. This allows us to document how representative the home locations of our users are and how smartphone users differ from other individuals. We then propose a number of metrics to measure high-frequency mobility. Our rich data allow us to characterize mobility at various spatial and temporal scales. We find that users are remarkably mobile in terms of the fraction of days seen at least 10km away from their home location, and the average distance for non-home location pings. Individuals residing in low-density locations are well linked to high-density locations. A significant fraction of visitors to the largest cities comes from non-urban areas. Finally, we examine how sensitive travel is to distance. We find that across a wide range of spatial and temporal scales our estimates are in line with previous gravity estimates in the literature.