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2006 NCHS Urban-Rural Classification Scheme for Counties

National Center for Health Statistics (NCHS) data systems are often used to study the association 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 the 3,141 U.S. counties and county-equivalents. The most urban category consists of large metropolitan central counties and the most rural category consists of nonmetropolitan noncore counties.

The county classifications are based on the following information: (1) the 2003 Office of Management and Budget (OMB) definitions of metropolitan and nonmetropolitan counties (with revisions through 2005); (2) the Rural-Urban Continuum Codes and the Urban Influence Codes classifications developed by the Economic Research Service of the U.S. Department of Agriculture; and (3) county-level data on several variables from Census 2000 and 2004 postcensal population estimates.

This classification scheme, unlike others that have been developed since 2003, separates large metropolitan counties into two categories: large metro central and large metro fringe. These two categories were created because of striking differences in several health measures between residents of these two types of counties.

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.

Methodology

Data files
File layout
ASCII file (347K)
SAS File (497K)

Related Links:

Bridged-race population estimates

Compressed Mortality File

Office of Management and Budget: Standards for defining metropolitan and micropolitan areas

Office of Management and Budget: December 2005 update of statistical area definitions

USDA Economic Research Service: Rural-Urban Continuum Codes

USDA Economic Research Service: Urban Influence Codes

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

This page last reviewed September 11, 2008