Columbia subject headings:
Social classes--United States.
United States--Social conditions--1960-1980.
United States--Social conditions--1980-2020.
Harvard subject headings:
Social classes--United States
United States--Social conditions--1980-2020
Princeton subject headings:
Social classes--United States.
United States--Social conditions--1960-1980.
United States--Social conditions--1980-2020.