Maybe money really does grow on trees. In his Per Square Mile blog, Tim De Chant has been looking at the relationship between inequality and forest cover. Trees turn out to be one of the many things in life that you don’t see much of if you aren’t rich. This isn’t entirely news; after all, one of the standard ways to describe an affluent suburb is “leafy.” But De Chant tracked down a 2008 study showing the actual economic correlation between dollars and trees. The demand curve, it turns out, is not very different from what you’d see for a Rolex watch. “For every 1 percent increase in per capita income,” De Chant discovered, “demand for forest cover increased by 1.76 percent.” And “when income dropped by the same amount, demand decreased by 1.26 percent.” Rich people have more trees than poor people, and rich cities have more trees than poor cities. 

That made De Chant wonder: Is income inequality like crop circles, i.e., can it be viewed from outer space? With a little help from Google Earth, he found that it is. Houston's Fourth Ward (home to the city’s poorest African Americans): Not a lot of trees. In a satellite image it looks kind of gray. Houston’s River Oaks (home to some of the richest people in Texas): Lots of trees. In a satellite image it looks very green. And so on. De Chant then invited readers to submit their own Google Earth matchups. Same pattern. If planet Earth is ever invaded by space aliens, they shouldn’t have any difficulty figuring out well before their spaceship lands where the best wine bars are.