Two discrete sociological theories explain and justify gentrification: one as an economic process (production-side theory); the other and as a social process (consumption-side theory). Both occur when the suburban gentry tire of the automobile-dependent urban sprawl style of life. These professionals, empty nest aged parents, and recent university graduates perceive attractiveness in the city center earlier abandoned during white flight—especially if the poor community possesses a transport hub and its architecture sustains the pedestrian traffic that allows the proper human relations impeded by (sub)urban sprawl.