The mystery of America's small groceries

My Twin Cities neighborhood is teeming with small, independent grocery stores. If locales without grocery access are food deserts, this is a food rainforest. A few blocks northeast of us there's an Asian market, equipped with an abundant produce section, a butcher counter, and a boggling variety of cooking sauces. Several blocks southwest is a more traditional corner store, stocked with snacks, some basics like milk and eggs, plus beer and cigarettes. Survey the whole neighborhood — an...