David Mekarski, the village administrator for the south Chicago suburb of Olympia Fields, told a startling story this week at the American Planning Association's annual conference about a debate he recently had with a restaurant official. Why, he wanted to know, wouldn't quality restaurants come to his mixed-race community, where the average annual household income is $77,000, above the county average?

The reply: "Black folks don’t tip, and so managers can’t maintain a quality staff. And if they can’t maintain a quality staff, they can’t maintain a quality restaurant.”

A gasp then rippled through the room in front of Mekarski. "This is one of the most pervasive and insidious forms of racism left in America today," he says.

There's a term for the phenomenon he's describing: retail redlining. The practice is a more recent and less studied variation on redlining as it's been historically recognized in the housing sector. In the context of retail, grocery stores, and restaurants, redlining refers to the "spatially discriminatory practice" of not serving certain communities because of their ethnic or racial composition, rather than their economic prospects.

It's a newer phenomenon in part because there are more upper-income minority communities in America today. Households that can afford the same stores and restaurants as comparable White communities now want to know where the retailers are. The practice is tricky to study, though, because these types of communities are still relatively few in number (with hard-to-find comparison communities), and because it's difficult to distinguish a retailer's "unconscious racism" from its legitimate business reasons for locating a store or a restaurant.