Get off your high horse, New Yorkers! City dwellers might do some environmental good by driving less and living in smaller spaces. But living in a city doesn't affect a person's carbon footprint as much as the amount that he or she buys.

It's simple: living in a city is just another consumption decision. City dwellers consume less, generally, when it comes to things like daily transportation and home climate control. But if they splash out on other things — clothes, plane trips, expensive sushi — they can easily cancel out the dent their location puts in their carbon footprint. And in cities, particularly cities like New York, there are plenty of opportunities to buy more stuff that the car-owning commuter would never shell out for.