You all know what a food desert is, right? It's a place where there aren't very many supermarkets. In fact, most often it's a place with no supermarkets, and almost always it's a poor neighborhood. But why do food deserts exist? Perhaps poor neighborhoods just aren't very profitable places to open supermarkets. But poor neighborhoods usually have plenty of bodegas and little corner shops, and if those places can make money why can't a supermarket? What's more, supermarket executives have always been very cagey when they're asked about the phenomenon, which suggests there's more to it than mere profitability. It's a bit of a mystery.