Columbia subject headings:
Central America--Economic conditions.
Central America--Population.
Labor supply--Central America.
Labor supply--Mexico.
Labor supply--Panama.
Latin America--Economic conditions.
Mexico--Economic conditions--1918-
Mexico--Population.
Harvard subject headings:
Central America--Economic conditions.
Central America--Population.
Labor supply--Central America.
Labor supply--Mexico.
Latin America--Economic conditions.
Mexico--Economic conditions--1918-
Mexico--Population.
Princeton subject headings:
Central America--Economic conditions.
Central America--Population.
Labor supply--Central America.
Labor supply--Mexico.
Latin America--Economic conditions.
Mexico--Economic conditions--1918-
Mexico--Population.