Top Lights: Bright Cities and Their Contribution to Economic Development
Dec 11, 2018
Richard Bluhm, Melanie Krause
Bluhm R. & Krause, M. (2018). Top Lights: Bright Cities and Their Contribution to Economic Development. AidData Working Paper #67. Williamsburg, VA: AidData at William & Mary.
Update: A revised version of this paper has been published in Journal of Development Economics.
Tracking the development of cities in emerging economies is difficult with conventional data. We show that satellite images of nighttime lights are a reliable proxy for economic activity at the city level, provided they are first corrected for top-coding. The commonly-used data fail to capture the true brightness of most cities. We present a stylized model of urban luminosity and empirical evidence which both suggest that these ‘top lights’ can be characterized by a Pareto distribution. We then propose a simple correction procedure which recovers the full distribution of city lights. Our results show that the brightest cities account for nearly a third of global economic activity. Applying this approach to cities in Sub-Saharan Africa, we find that primate cities are outgrowing secondary cities but are changing from within. Poorer neighborhoods are developing and sub-centers are emerging, with the side effect that Africa’s largest cities are also becoming increasingly fragmented.
Funding: The authors gratefully acknowledge financial support from the German Science Foundation (DFG).