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.
This page last reviewed
September 11, 2008