Urbanization Level

Urbanization is the degree of urban (city-like) character or nature of a particular geographic area. Numerous classification schemes have been devised to categorize counties and county equivalents by urbanization level.  Many urbanization classification schemes make use of the Office of Management and Budget’s (OMB) metropolitan/nonmetropolitan designation for counties.  A metropolitan area is defined by OMB to be a county or group of counties that contain a core urban area of 50,000 or more population together with adjacent counties having a high degree of economic and social integration with that core.  OMB classifies all counties within a metropolitan area as metropolitan.  All counties not within a metropolitan area are considered nonmetropolitan and beginning with the 2000 OMB standards are further subdivided into two distinct types of counties, micropolitan and nonmicropolitan.  A micropolitan statistical area contains a core urban area of at least 10,000 (but less than 50,000) population. Each micropolitan area consists of one or more nonmetropolitan counties and includes the counties containing the core urban area, as well as any adjacent counties that have a high degree of social and economic integration (as measured by commuting to work) with the urban core.

NCHS has developed a county-level urbanization classification scheme based on the 2000 OMB standards for defining metropolitan and micropolitan areas and on the 2000 census.  The NCHS Urban-Rural Classification scheme  divides the 3,141 U.S. counties and county equivalents into six categories, four metropolitan and two nonmetropolitan. The metropolitan categories are defined using the population size cut points used by the Economic Research Service, U.S. Department of Agriculture for the 2003 Rural-Urban Continuum Codes (50,000 to 249,999; 250,000 to 999,999; and 1 million or more).  The NCHS classification also subdivides counties in the largest metropolitan areas (1 million or more population) into two subcategories, central and fringe.  The two nonmetropolitan levels of the NCHS classification, micropolitan and noncore (nonmicropolitan), are derived directly from the differentiation of nonmetropolitan territory specified in the 2000 OMB standards.

Metropolitan categories
Large Central - Central counties in metro areas of 1 million or more population
Large Fringe - Outlying (suburban) counties in metro areas of 1 million or more population
Medium - Counties in metro areas of 250,000-999,999 population
Small - Counties in metro area of 50,000-249,999 population

Nonmetropolitan categories
Micropolitan - Counties in an area with an urban cluster of 10,000-49,999 population
Noncore - Nonmicropolitan

SOURCE: 2006 NCHS Urban-Rural Classification Scheme for Counties

Related Links
2006 NCHS Urban-Rural Classification for Counties
Metropolitan Statistical Area
Micropolitan Statistical Area

This page last reviewed January 11, 2007