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 the standard building block for collecting economic data and for conducting research to track and explain regional population and economic trends. Nonmetro counties (see the map below) include some combination of:
- open countryside,
- rural towns (places with fewer than 2,500 people), and
- urban areas with populations ranging from 2,500 to 49,999 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. Census Bureau uses much smaller geographic building blocks to define rural areas as open country and settlements with fewer than 2,500 residents. 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:
In addition, ERS has created files designed for use with the American Community Survey’s Public Use Microdata Sample (ACS-PUMS) that enable rural researchers and others who work with household or person-level survey data to better classify areas as metro/nonmetro. The files identify each Public Use Microdata Area (PUMA) in the ACS-PUMS as either metro, nonmetro, or mixed, based on the metro and nonmetro population shares in each PUMA; for mixed PUMAs, the share of the population residing in a metro area is reported. See the ZIP file for the data files (to match to 2000 or 2010 PUMA geography), Stata files with technical details, and documentation including population counts and summaries. See Identifying the Metro-Nonmetro Status of Public Use Microdata Areas.