Analysis of 1970 to 2000 decennial census data for families and neighborhoods in the 100 largest metropolitan areas, and in the cities and suburbs of 12 selected metropolitan areas, finds that: Middle-income neighborhoods as a proportion of all metropolitan neighborhoods declined from 58 percent in 1970 to 41 percent in 2000. This dramatic decline far outpaced the corresponding drop in the proportion of metropolitan families earning middle incomes, from 28 percent in 1970 to 22 percent in 2000.