Labor force is the segment of a nation's population that works for pay or is actively seeking work. This group produces most of the nation's goods and services, and its size and productivity help determine the nation's economic growth. The United States labor force expanded from about 2 million in 1800 to about 140 million in 2005. During this period, it changed from a mainly agricultural one to one composed mainly of industrial, service, and white-collar workers.