Researchers analysed two separate datasets from satellites: the first showed images of all the areas of the world that light up at night, and the second estimated population using images of roads, buildings and other signs of human habitation. Both satellites covered every square kilometre around the world, amounting to 100 million data points every year. By combining the two datasets into one, the researchers identified places in the world where populations have no night-time lights. They find this accurately identifies people in poverty after comparing it with over 600,000 household surveys, and is faster, cheaper and has better coverage than the surveys typically used to measure poverty.
The study shows that oil booms increase inequality and do not benefit the rural poor. The benefits of oil discoveries and high oil prices appear to be limited to towns and cities, which become more illuminated (which the researchers use as a proxy for greater economic activity). However, there is no evidence of a wealth trickle-down effect, as the areas where the rural poor live remained unlit through a decade of high oil prices (2003-2013).