From Economist Free Exchange:
Pictures of the day | Free exchange | Economist.com: OVER at Vox, J. Vernon Henderson, Adam Storeygard, and David N. Weil write that images of the earth at night can be used to refine GDP data for places that stuffer from poor on the ground data collection. The secret is in the lights.... What you're looking at there is a slice of central and eastern Europe. On the left side of both images is Poland and portions of Slovakia and Hungary. From the middle to the right of the images you have Belarus, Ukraine, and Moldova. And what you can observe is the significant difference in the economic fortunes of former Soviet bloc economies in the decade after the dissolution of the USSR. The western side gets much brighter, and the east, dimmer, reflecting the problematic transitions in eastern Europe.