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NCHS Urban-Rural Classification Scheme for Counties

National Center for Health Statistics (NCHS) data systems are often used to study the associations between urbanization level of residence and health and to monitor the health of urban and rural residents. NCHS has developed a six-level urban-rural classification scheme for U.S. counties and county-equivalent entities. The most urban category consists of "central" counties of large metropolitan areas and the most rural category consists of nonmetropolitan "noncore" counties. Three versions of the NCHS scheme are available:

  1. 2013 NCHS Urban-Rural Classification Scheme for Counties which is based on the Office of Management and Budget’s (OMB) February 2013 delineation of metropolitan statistical areas (MSA) and micropolitan statistical areas (derived according to the 2010 OMB standards for defining these areas) and Vintage 2012 postcensal estimates of the resident U.S. population;
  2. 2006 NCHS Urban-Rural Classification Scheme for Counties which is based on the OMB’s December 2005 delineation of MSAs and micropolitan statistical areas (derived according to the 2000 OMB standards for defining these areas) and  Vintage 2004 postcensal estimates of the resident U.S. population), and
  3. 1990 census-based NCHS Urban-Rural Classification Scheme for Counties which is based on the OMB’s June 1993 delineation of MSAs (derived according to the 1990 OMB standards for defining these areas) and 1990 census data.

The levels of the NCHS scheme were chosen for their utility in studying health differences across the urban-rural continuum. The NCHS scheme has more metropolitan levels (four) than nonmetropolitan levels (two) because the large U.S. metropolitan population (in 2010, about 85% of the U.S. population) can support more levels for health analyses than the relatively small nonmetropolitan population. 

The basic framework of the three schemes is the same. However, while the classification rules used to assign counties to the six urban-rural categories are the same for the 2013 and 2006 NCHS schemes, they differ somewhat from those used for the 1990 census-based scheme.

A key feature of the NCHS urban-rural scheme, which makes it particularly well-suited for health analyses, is that it separates counties within large metropolitan areas (1 million or more population) into two categories: large "central" metro (akin to inner cities) and large "fringe" metro (akin to suburbs). This is an important feature of the NCHS urban-rural scheme because for a number of health measures, residents of large fringe metro areas fare substantially better than residents of other urbanization levels. For these measures, residents of the inner cities and suburbs of large metropolitan areas must be differentiated to obtain an accurate characterization of health disparities across the full urban-rural spectrum.

The report 2013 NCHS Urban–Rural Classification Scheme for Counties [PDF - 2.5 MB] details development of the 2013 NCHS scheme and provides some examples o the scheme's application to mortality data and to health measures from the National Health Interview Survey. The report also compares the 2013 and 2006 NCHS schemes.

The report NCHS Urban–Rural Classification Scheme for Counties [PDF - 1.3 MB] details development of the 2006 NCHS scheme and provides some examples of the scheme's application to mortality data and to health measures from the National Health Interview Survey. The report also describes the 1990 census-based NCHS scheme.

 

2013 Urban-Rural Classification Scheme for Counties

 This map shows all U.S. counties and their classification under the 2013 NCHS Urban-Rural Classification Scheme for Counties. Large central metro counties are red, large fringe metro counties are orange, medium metro counties are yellow, small metro counties are white, micropolitan counties are light green, and noncore counties are dark green. The map illustrates that the eastern half of the United States is more densely settled than the western half. It also illustrates differences in county size, smaller counties east of the Mississippi river and larger counties west  of the river.

Metropolitan counties: Large central metro counties in MSA of 1 million population that: 1) contain the entire population of the largest principal city of the MSA, or 2) are completely contained within the largest principal city of the MSA, or 3) contain at least 250,000 residents of any principal city in the MSA.
Large fringe metro counties in MSA of 1 million or more population that do not qualify as large central Medium metro counties in MSA of 250,000-999,999 population.
Small metro counties are counties in MSAs of less than 250,000 population.
Nonmetropolitan counties: Micropolitan counties in micropolitan statistical area; Noncore counties not in micropolitan statistical areas data access website

 

2006 Urban-Rural Classification Scheme for Counties

 

This map shows all U.S. counties and county equivalents and their classification under the 2006 NCHS Urban-Rural Classification Scheme for Counties.  Large central metro counties are red, large fringe metro counties are orange, medium metro counties are yellow, small metro counties are white, micropolitan counties are light green, and noncore counties are dark green. The map illustrates that the eastern half of the United States is more densely settled than the western half. The map also illustrates the differences in county size -- smaller counties east of the Mississippi and larger counties west of the Mississippi.
Metropolitan counties: Large central metro counties are counties in metropolitan statistical areas (MSA) of 1 million or more population that 1) contain the entire population of the largest principal city of the MSA, or 2) are completely contained in the largest principal city of the MSA, or 3) contain at least 250,000 residents of any principal city of the MSA. Large fringe metro counties are counties in MSAs of 1 million or more population that do not qualify as large central. Medium metro counties are counties in MSAs of 250,000 to 999,999 population. Small metro counties are counties in MSAs of less than 250,000 population.
Nonmetropolitan counties: Micropolitan counties are counties in micropolitan statistical areas. Non-core counties are nonmetropolitan counties that are not in a micropolitan statistical area.

 

Use of the Urban-Rural Classification with Natality and Mortality Files

The NCHS Urban-Rural Classification Scheme for Counties should only be used with data files where all counties are identified. Standard mortality and natality public-use files do not identify counties with populations less than 100,000. Specifically, the county FIPS codes for counties with populations less than 100,000 are not provided on these files; instead all of these counties are assigned the same geographic code for “balance of state.” Because there are counties with populations less than 100,000 in all of the urban-rural categories except the large central metro category, it is not possible to compute birth and death rates by urbanization level using the standard natality and mortality public-use files. Access to mortality and natality files with all counties identified currently requires NCHS approval of the project and the signing of a data user’s agreement.

 

Data Files and Documentation

 

Contact

National Center for Health Statistics
Office of Analysis and Epidemiology
Room 6211
3311 Toledo Road
Hyattsville, MD 20782
Email: popest@cdc.gov

 

 

 
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