Take a look at this map depicting the U.S. at night. What should be immediately obvious is that there are a lot of bright lights exactly where the richest people live: the East Coast megalopolis from Boston through Washington, D.C., Midwestern burgs such as Chicago, Southern cities such as Atlanta and the West Coast conurbation that goes by the name Los Angeles.

Inspired by this association—and others revealed in night time images that stretch back to the mid-1960s taken by the U.S. Department of Defense—economists, sociologists and other scientists with an interest in economic development have begun to explore whether nighttime lights might help reveal the relative richness of regions for which standard economic data is lacking. With that in mind economist William Nordhaus of Yale University and sociologist Xi Chen of Quinnipiac University parsed "luminosity" data from 1992 to 2008 for a wide range of countries world-wide—and even sub-regions within those countries.

In order to determine whether the extent of night lighting provided accurate economic data, the researchers first compared lighting levels with other economic statistics from countries that provide relatively reliable information, such as Australia, Canada and the U.S. Luminosity matched up well with other statistics and, therefore, failed to add much "new" information to existing economic statistics for those nations even at the regional level.

But for 29 countries—including, for example, the Democratic Republic of Congo, which is war-torn and has no reliable statistics despite covering more land than Western Europe—luminosity proved a revealing indicator of economic progress that was otherwise unknown.

Of course, there are countries that have some level of economic activity despite a lack of significant night lights. For example, when spending the night in Dandong on the Chinese-North Korean border, you would notice that an array of bright neon lights color the night, even extending across the two countries' Friendship Bridge from China to North Korea. But the North Korean side is dark, except for the occasional floodlight to detect those who would ford or swim the Yalu River. That doesn't mean that there is no economic activity in North Korea, just that North Korea's government starves its people of electricity as well as food. Alleviating such "light" (read: energy) poverty—endured by roughly one billion people on the planet—remains a key development goal for those interested in ending human suffering.

More than 70 percent of the globe falls into this "dark" category by landmass, where man-made light goes largely undetected by satellites. That means luminosity may not prove useful for the most benighted places on the planet, but could help begin to pierce the darkness surrounding the economic activity of those countries struggling to develop.

Image: Courtesy of NOAA