Neighborhood Gentrification

“Sorry about this mess, I don’t want to drive down your property values!” exclaims the young hostess, tripping over stray sheetrock and spackling compound toward 30 members of the new block association gathered stiffly in her living room—including a few minority tenants who’d be relieved at the moment to have property values to worry about.

Learning that one of the young professionals has been living on the block for ten years, the hostess trumpets, “You...