A black map of the world with white showing most lit areas
Vernon Henderson & Adam Storeygard & David N. Weil, 2012. 'Measuring Economic Growth from Outer Space', American Economic Review, American Economic Association, vol.102(2), pp.994–1028, April

When the sun sets just after 18.00 in her village 50km West of Addis Adaba, Tsehay has much less than an hour to clear up before it becomes pitch dark. Her two young sons’ play stops, her eldest daughter has to close her book and her husband will have to wait to fix his hoe until tomorrow. Only 1 in 5 Ethiopians have access to electricity. Once night sets in, Africa is again the Dark Continent. 

Night-time satellite pictures can be used to measure the glow or radiance of human induced light. Pictures of Africa show pockets of high luminosity across South Africa, bits of North-Africa and some coastal areas in countries such as Ghana or Nigeria. But huge tracks of African land can’t escape from the night.

Light matters. Long hours each day are lost in darkness. Children cannot read or draw or play. Work stops. Economic activity stops. Less is made, less is sold, less is bought.  Life has to stop for the night.

No light does not cause poverty; it is poverty.

So it should not come as a surprise that economists have found that the wealth and economic activity of countries is well approximated by night-time luminosity as seen from outer space. Over time, these pictures tell us the story of growth and development. Across the earth, they paint the picture of the huge inequalities in the world. And small dots of light in dark spaces tell us the story of hope.

Stefan Dercon
Chief Economist, UK Department of International Development
Professor of Development Economics, Oxford University.