The Population Seen from Space: When Satellite Images Come to the Rescue of the Census

Mathias Kuepie, Independent consultant in Population, Statistics and Socio-economic studies
Edith Darin, University of Oxford
Hervé Bassinga, Institut Supérieur des Sciences de la Population (ISSP) / Université de Ouagadougou
Gianluca Boo, University of Southampton
Andrew J. Tatem, University of Southampton

The size of the population, the denominator of many statistical indicators, is crucial for public policy. National statistical offices organize the collection of this information, most often through a census. But what happens when parts of a country are not accessible to census enumerators? Today, spatial data extracted from satellite imagery offer high-resolution geographical information with complete coverage. When combined with a partial population count, they offer an unprecedented opportunity to estimate the size of the population in inaccessible areas. Based on the case of Burkina Faso, this article analyses how, by dividing a country into 100 m by 100 m cells, a Bayesian hierarchical model can be used to estimate the population of areas with security challenges which could not be enumerated during the 2019 census. This gridding allows the resulting counts to be disaggregated using a statistical learning model, yielding unparalleled spatial precision in population estimates.