USDA, Economic Research Service (ERS) researchers and others who analyze conditions in "rural" America most often study conditions in nonmetropolitan (nonmetro) areas, defined on the basis of counties. Counties are a standard geographic unit for collecting economic data and for conducting research to track and explain regional population and economic trends. Nonmetro counties include some combination of:
- open countryside,
- rural towns (places with fewer than 5,000 people and 2,000 housing units), and
- urban areas with populations ranging up to 50,000 people that are not part of larger labor market areas (metropolitan areas).
In addition to conducting research that uses the basic metro-nonmetro dichotomy, ERS has developed multi-level county classifications to measure rurality in more detail and to assess the economic and social diversity of nonmetro America. Some of these classification schemes have been used to determine eligibility for Federal programs that assist rural areas. They include the:
- Rural-Urban Continuum Codes,
- Urban-Influence Codes,
- Natural Amenities Scale, and the
- ERS Typology Codes, which classify rural counties by their economic and policy types.
For some research and program applications, counties are too large to accurately distinguish rural and urban settlement patterns. The U.S. Department of Commerce, Bureau of the Census uses much smaller geographic building blocks to define rural areas as open country and settlements with fewer than 5,000 residents and fewer than 2,000 housing units.
Most counties, whether metro or nonmetro, contain a combination of urban and rural populations.
Building on the urban-rural definition, ERS has developed sub-county classifications that more accurately delineate different levels of rurality and address program eligibility concerns. They include the:
