 Since the 1950s America's urban centers have suffered from pervasive social problems, exacerbated by the loss of working and middle class households, creating concentrations of extreme wealth and poverty.Urban redevelopment has enhanced the economic base of cities like with new office buildings and entertainment venues, hotels and tourist areas, and upscale apartment buildings.But without successful schools, safe playgrounds and neighborhoods, and other basic amenities, cities have failed to compete with neighboring suburbs to attract and retain moderate income residents.