The United States Office of Management and Budget (OMB) delineates metropolitan and micropolitan statistical areas according to published standards that are applied to Census Bureau data. The general concept of a metropolitan or micropolitan statistical area is that of a core area containing a substantial population nucleus, together with adjacent communities having a high degree of economic and social integration with that core.
Definitions
The term “core based statistical area” (CBSA) became effective in 2000 and refers collectively to metropolitan and micropolitan statistical areas. The 2010 standards provide that each CBSA must contain at least one urban area of 10,000 or more population. Each metropolitan statistical area must have at least one urbanized area of 50,000 or more inhabitants. Each micropolitan statistical area must have at least one urban cluster of at least 10,000 but less than 50,000 population. Combined statistical areas (CSAs) are aggregates of adjacent metropolitan or micropolitan statistical areas that are linked by commuting ties.
Counties or equivalent entities form the geographic “building blocks” for metropolitan and micropolitan statistical areas throughout the United States and Puerto Rico. Under the standards, the county (or counties) in which at least 50 percent of the population resides within urban areas of 10,000 or more population, or that contain at least 5,000 people residing within a single urban area of 10,000 or more population, is identified as a “central county” (counties). Additional “outlying counties” are included in the CBSA if they meet specified requirements of commuting to or from the central counties.
If specified criteria are met, a metropolitan statistical area containing a single core with a population of 2.5 million or more may be subdivided to form smaller groupings of counties referred to as “metropolitan divisions.”
The largest city in each metropolitan or micropolitan statistical area is designated a “principal city.”
In view of the importance of cities and town in New England, the 2010 standards also provide for a set of geographic areas that are delineated using cities and towns in the six New England states. The New England city and town areas (NECTAs) are delineated using the same criteria as metropolitan and micropolitan statistical areas. Similarly to CBSAs, there are metropolitan and micropolitan NECTAs, combined NECTAs, and NECTA divisions.
Delineation revisions
A metropolitan or micropolitan statistical area’s geographic composition, or list of geographic components at a particular point in time, is referred to as its “delineation.” Metropolitan and micropolitan statistical areas are delineated by the U.S. Office of Management and Budget (OMB) and are the result of the application of published standards to Census Bureau data. The standards for delineating the areas are reviewed and revised once every ten years, prior to each decennial census. Generally, the areas are delineated using the most recent set of standards following each decennial census. Between censuses, the delineations are revised to reflect Census Bureau population estimates and–once each decade–updated commuting-to-work data. Areas based on the 2010 standards and Census Bureau data were delineated in February of 2013, and updated in July of 2015, August of 2017, April of 2018, September of 2018, and March of 2020.
Changes in the delineations of these statistical areas since the 1950 census have consisted chiefly of: - the recognition of new areas as they reached the minimum required urban area or city population, and - the addition of counties (or cities and towns in New England) to existing areas as new commuting and urban area data showed them to qualify.
In some instances, formerly separate areas have been merged, components of an area have been transferred from one area to another, or components have been dropped from an area. The large majority of changes have taken place on the basis of decennial census (and more recently American Community Survey) data. However, Census Bureau Population Estimates Program and American Community Survey data serve as the basis for intercensal updates in specified circumstances.
List of available revisions
Revision
Census
Mar 2020
2010
Sep 2018
2010
Apr 2018
2010
Aug 2017
2010
Jul 2015
2010
Feb 2013
2010
Dec 2009
2000
Nov 2008
2000
Nov 2007
2000
Dec 2006
2000
Dec 2005
2000
Nov 2004
2000
Dec 2003
2000
Jun 2003
2000
Jun 1999
2000*
Jun 1993
1990**
Jun 1990
1990*
Jun 1983
1980**
Jun 1981
1980*
Apr 1973
1980**
Feb 1971
1970*
Oct 1963
1960**
Nov 1960
1960*
Oct 1950
1950*
* Delineations used for presenting metropolitan area statistics in upcoming Census publications.
** Delineations based on application of metropolitan area standards to preceding census data.
Delineation tables
Function get_cbsa_delin_df(year) returns delineation dataframe for a chosen year.
Examples
From 2020 CBSA delineation.
Combined statistical area (CSA) “Madison-Janesville-Beloit, WI” consists of three core based statistical areas (CBSAs): two metropolitan statistical areas (“Madison, WI” and “Janesville-Beloit, WI”) and one micropolitan statistical area (“Baraboo, WI”). No divisions exist within CBSAs, because neither CBSA has core of greater than 2.5 million people. “Madison, WI” metro area consists of the central Dane county and three adjacent outlying counties - Columbia, Green and Iowa.
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CBSAs of Wisconsin, 2021.
New England
New England city and town areas (NECTAs) are an alternative delineation available for the six states of New England that uses county subdivisions as building blocks. Consequently, NECTA boundaries can cross county boundaries, as shown in the map below.