Map of National (and Some States/Provinces) Wealth...

Wealth of a country (or other geopolitical entity) is a notoriously slippery datum to measure.  It isn't enough to convert per capita income to a common currency and compare them, because the cost of living varies tremendously from place to place.  Furthermore, in some political systems (I'm looking at you, Mother Russia, Mexico, China, Nigeria, India, et al), pervasive corruption means that significant fractions of their economies are underground and therefore not even in the official per capita income data.  What's a poor statistician to do?

One possibility is to find a proxy for that which you're trying to measure.  Ideally the proxy would be perfectly proportional to the value you actually want to measure, and could be measured without perturbing the value you're trying to measure.  In the case of the wealth of countries, some scientists have proposed the prevalence of outdoor artificial lighting at night as a proxy.  Their thinking is that the wealthier any country is, the more outdoor artificial lighting they'll use.  And very conveniently, outdoor lighting levels can be easily measured by existing satellites, hundreds of which image the surface of the earth every day.

The map below is the result of an attempt to make exactly this measurement.  As I cast my eye over the map, relatively few of the results look unexpected to me.  For instance, I wouldn't have guessed Greenland was so prosperous, nor Paraguay so poor.