“The border between desirable and undesirable ran in a ragged irregular loop, bulging outward here and there to accommodate reclaimed blocks, swooping inward in other areas to claim inroads of its own. It was pierced in some places by gentrified corridors. Elsewhere it worked gradually, shading imperceptibly over hundreds of yards down streets where you could buy thirty different blends of tea at one end and cash checks at the other for thirty percent of the”