Low-income families: fertility changes in the 1960s.
D000293:Adolescent; D000328:Adult; D001723:Birth Rate; D005191:Family Characteristics; D005193:Family Planning Services; D005260:Female; D005298:Fertility; D006801:Humans; D011203:Poverty; D044469:Racial Groups; D014481:United States; D014505:Urban Population