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Measuring Rurality: Urban Influence Codes

Contents
 
Contents
 

An area's geographic context has a significant effect on its development. Economic opportunities accrue to a place by virtue of both its size and its access to larger economies. And, access to larger economies—centers of information, communication, trade, and finance—enables a smaller economy to connect to national and international marketplaces. These relationships among economies are basic concepts of the central place theory commonly studied in regional economics. Population size, urbanization, and access to larger communities are often crucial elements in research dependent on county-level data sets. To further such research, ERS developed a set of county-level urban influence categories that captures some differences in economic opportunities.

The 2003 Urban Influence Codes divide the 3,141 counties, county equivalents, and independent cities in the United States into 12 groups. Metro counties are divided into two groups by the size of the metro area—those in "large" areas with at least 1 million residents and those in "small" areas with fewer than 1 million residents. Nonmetro micropolitan counties are divided into three groups by their adjacency to metro areas—adjacent to a large metro area, adjacent to a small metro area, and not adjacent to a metro area. Nonmetro noncore counties are divided into seven groups by their adjacency to metro or micro areas and whether or not they have their "own town" of at least 2,500 residents. Census-defined places are considered to be towns in this classification. Independent cities of Virginia have been combined with their counties of origin, and Kalawao County Hawaii has been combined with Maui County.

Urban influence codes group metro and nonmetro counties according to the official metro status announced by the Office of Management and Budget (OMB) (See new definitions in 2003 for more information) in June 2003, based on population and commuting data from the 2000 Census of Population. Nonmetro counties are defined as adjacent if they abut a metro area (noncore also if they abut a micro area) and have at least 2 percent of employed persons commuting to work in the core of the metro area (or in the micro area). When a nonmetro county met the adjacency criteria to more than one metro (or micro) area, it was designated as adjacent to the area to which the largest percentage of its workers commuted.

County-level map showing the 2003 Urban Influence Codes.

2003 Urban Influence Codes
Code Description
Number of counties
2000 Population
Square miles
Population per sq. mile
Metropolitan counties:
1
In large metro area of 1+ million residents
413
149,224,067
267,423
558.0
2
In small metro area of less than 1 million residents
676
83,355,873
629,671
132.4
Nonmetropolitan counties:
3
Micropolitan area adjacent to large metro area
92
5,147,233
94,178
54.7
4
Noncore adjacent to large metro area
123
2,364,159
88,229
26.8
5
Micropolitan area adjacent to small metro area
301
14,668,144
285,527
51.4
6
Noncore adjacent to small metro area and contains a town of at least 2,500 residents
358
7,855,590
334,361
23.5
7
Noncore adjacent to small metro area and does not contain a town of at least 2,500 residents
185
1,879,264
336,499
5.6
8
Micropolitan area not adjacent to a metro area
282
9,139,821
338,256
27.0
9
Noncore adjacent to micro area and contains a town of at least 2,500 residents
201
3,227,833
193,200
16.7
10
Noncore adjacent to micro area and does not contain a town of at least 2,500 residents
198
1,313,175
196,269
6.7
11
Noncore not adjacent to metro or micro area and contains a town of at least 2,500 residents
138
2,247,189
488,521
4.6
12
Noncore not adjacent to metro or micro area and does not contain a town of at least 2,500 residents
174
999,558
285,304
3.5
Total U.S.
3,141
281,421,906
3,537,438
79.6

Description of the 1993 Urban Influence Codes.

In concept, the 2003 version of the Urban Influence Codes is comparable with those of earlier decades. However, OMB made major changes in its metro area delineation procedures for the 2000 Census, and the Census Bureau changed the way in which rural and urban are measured. Therefore, the new Urban Influence Codes are not fully comparable with those of earlier years. OMB's changes added some additional metro areas by no longer requiring that a metro area must have at least 100,000 population if its urbanized area has no place of at least 50,000 people. More importantly, simplifying the worker commuting criteria that determine outlying metro counties had the effect of both adding numerous new outlying counties to metro status while deleting a smaller number that were previously metro.

The Census Bureau made a radical shift in determining rural-urban boundaries by changing and liberalizing the procedures for delineating urbanized areas of 50,000 or more people, and abandoning place boundaries in measuring urban or rural population (See what is rural? for more information). The procedures used in defining Urbanized Areas were extended down to clusters of 2,500 or more people, based solely on population density per square mile. In this manner, lightly settled sections of municipalities were treated as rural, and densely settled areas adjoining urban cores were treated as urban, regardless of whether they were incorporated or not. Thus "urban clusters" need not necessarily have at least one incorporated or unincorporated place of 2,500 population, and not all incorporated or unincorporated places of 2,500 population constitute urban clusters. On balance, these completely computerized techniques for identifying and bounding urban areas have enlarged the urban population. It is not possible to redefine Urban Influence Codes for prior censuses in a manner consistent with those of 2003.

 

For more information, contact: Tim Parker

Web administration: webadmin@ers.usda.gov

Updated date: August 8, 2007