This map uses data from the U.S. Air Force Defense Meteorological Satellite Program (DMSP) Operational Line-Scan System (OLS) Version 4. Using their cloud-free average of the visible band's digital number values (values ranging between 1 and 63), I performed a linear regression on annual averages between 1992 and 2013. The resulting map presents the slope of the linear regression. Areas with positive values indicate areas experiencing increased night light activities.

Ephemeral events, such as fires, have been discarded and background noise filtered.