Table 1.

Rural definitions

DefinitionDefinition descriptionGeographic unit usedPros and cons for cancer research
U.S. Census Bureau: Urban and Rural AreasThe Census Bureau's classification of rural consists of all territory, population, and housing units located outside of urbanized areas and urban clusters. Urbanized areas include populations of at least 50,000, and urban clusters include populations between 2,500 and 50,000. The core areas of both urbanized areas and urban clusters are defined based on population density of 1,000 per square mile and then certain blocks adjacent to them are added that have at least 500 persons per square mile.Census Block and Block GroupsPros: Census geography is more stable than ZIP code areas due to the fact that it changes over 10-year intervals rather than annually. Census geography is also the smallest geographic unit available. Cons: It is difficult to implement census definitions of rural because census geographical information is not often used by programs such as Medicare, Medicaid, and insurance companies.
Economic Research Service, U.S. Department of Agriculture & WWAMI Rural Health Research Center: RUCAsThis classification scheme utilizes the U.S. Census Bureau's urbanized area and cluster definitions and work commuting information. The RUCA categories are based on the size of settlements and towns as delineated by the Census Bureau and the functional relationships between places as measured by tract-level work commuting data. This taxonomy defines 33 categories of rural and urban census tracts.Census Tract, ZIP Code approximation availablePros: RUCAs encompass population density, urbanization, and daily commuting. This method provides a measure of functional relationships while using a more specific geographic unit than the OMB's taxonomy. If using the ZIP code approx. - ZIP code areas are more geographically specific than boundaries created by county lines. ZIP codes are also easier to use with programs that rely on the provider/beneficiary address.
Cons: (see above for census tract) If using the ZIP code approximation- ZIP codes often change annually.
U.S. Office of Management and Budget (OMB): Core-based statistical areas (i.e., metropolitan and non-metropolitan areas)A metropolitan area contains a core urban area with a population of 50,000 or more. Non-metropolitan counties are outside the boundaries of metropolitan areas and are subdivided into two types, micropolitan areas and noncore counties. Micropolitan areas are urban clusters with a population of at least 10,000, but less than 50,000.CountyPros: National health data sets use counties as their geographic unit and county boundaries remain very stable over time.Cons: County size varies and larger counties may include both urban and rural areas.
Economic Research Service, U.S. Department of Agriculture: Rural–Urban Continuum Codes (Beale Codes)This classification scheme classifies counties and county equivalents OMB metropolitan–non-metropolitan status and then further subdivides into three metropolitan and six nonmetropolitan groupings by the population size of the metropolitan area and adjacency to another metropolitan areas.CountyPros: RUCCs, like RUCAs, also distinguish counties by size, degree of urbanization, and proximity to metropolitan areas. RUCCs take into account the OMB categories and subdivide them further which can help to minimize the effects of variations in county size.
Cons: (see above for OMB)
Office of Rural Health Policy, U.S. Department of Health and Human Services: RUCA adjustment to OMB metropolitan and non-metropolitan definitionThis method uses RUCAs 4–10 to identify small towns and rural areas within large metropolitan counties. In addition, census tracts within metropolitan areas with RUCA codes 2 and 3 that are larger than 400 square miles and have population density of less than 30 people per square mile are also considered rural.Census tract within OMB metropolitan countiesPros: This method uses the metropolitan counties defined by the OMB in addition to RUCAs, to create a more specific definition and to define the rural/urban areas that may exist within a large metropolitan county. Cons: It is difficult to implement census definitions of rural because census geographical information is not often used by programs such as Medicare, Medicaid, and insurance companies.
ARIA: Accessibility/Remoteness Index of AustraliaThis method defines five categories of remoteness based on road distance to service centers (urban areas with a population of 5,000 or more), and is available for a variety of geographical units including localities, Census collection districts, statistical local areas(SLA)/local government areas(LGA) and postcodes.A variety of Australian government unitsPros: ARIAs, similar to RUCAs, encompass population density, urbanization, and daily commuting. Cons: County size defined by the boundaries created by the SLAs and LGAs may vary and can contain both rural and urban areas.