Columbia subject headings:
Age and employment--United States.
Industrial organization--United States.
Social classes--United States.
Wages--United States.
Harvard subject headings:
Age and employment--United States.
Industrial organization--United States.
Social classes--United States
Wages--United States.
Princeton subject headings:
Age and employment--United States.
Industrial organization--United States.
Social classes--United States.
Wages--United States.