Over the past three decades, the concentration of poverty in America's inner cities has exacerbated a wide range of social problems. School delinquency, school dropout, teenage pregnancy, out-of-wedlock childbirth, violent crime, and drug abuse are magnified in neighborhoods where the majority of residents are poor. In response, policymakers have embarked on a large and coordinated effort to "deconcentrate" the urban poor by dispersing the residents...