Columbia subject headings:
Households--Economic aspects--United States.
Middle class--United States--Economic conditions.
United States--Economic conditions--2009-
Harvard subject headings:
Families--Economic aspects--United States.
Middle class--United States--Economic conditions.
United States--Economic conditions--2009-
United States--Social conditions--21st century.
Princeton subject headings:
Households--Economic aspects--United States.
Middle class--United States--Economic conditions.
United States--Economic conditions--2009-