Note
We use the Version 4 DMSP-OLS Nighttime Lights Time Series for the data from 1992 to 2013 [2], combined with the DMSP Nighttime Lights Extension for the period 2014 to 2021 [3]. We extracted the sum of the NTL values within a buffer of 10 km radius drawn around the centroids of the capital cities of low-income countries. The extraction was done with the ArcGIS software.
[2] Baugh, K., Elvidge, C. D., Ghosh, T., & Ziskin, D. (2010). Development of a 2009 stable lights product using DMSP-OLS data. Proceedings of the Asia-Pacific Advanced Network, 30(0), 114.
[3] Ghosh, T.; Baugh, K.E.; Elvidge, C.D.; Zhizhin, M.; Poyda, A.; Hsu, F.-C. Extending the DMSP Nighttime Lights Time Series beyond 2013. Remote Sens. 2021, 13, 5004.