Core Based Statistical Areas

Core Based Statistical Areas

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July 3, 2024
Core Based Statistical Areas
Core Based Statistical Areas (CBSAs) is the collective term
wage index). Federal agencies that use CBSAs for
used to refer to metropolitan statistical areas and
nonstatistical purposes do not make revisions to the OMB
micropolitan statistical areas, which are delineated by the
delineations. Nonstatistical uses of CBSAs have attracted
Office of Management and Budget (OMB). OMB generally
congressional interest.
defines a CBSA as an area that contains a central county
that has a substantial urban population, along with any
Figure 1 provides an example of CBSA delineations in
adjacent communities that have a high level of integration
New Hampshire based on OMB Bulletin No. 23-01
with the central county. In 2020, OMB defined CBSAs to
(discussed later in this product).
consist of a county or multiple counties (or other equivalent
entities) that contain a core urban area with a minimum
Figure 1. Core Based Statistical Areas Visualization
population of 10,000.
CBSAs of New Hampshire using revised delineations
published in OMB Bul etin No. 23-01
Core urban areas may have adjacent outlying counties that
have social and economic integration as measured through
commuting ties. Outlying counties are defined based on
residents who work in central counties of a CBSA or
workers who live in the central county but work in the
outlying county of a CBSA. A single CBSA may extend
beyond a single state’s borders.
The largest city in a CBSA is designated as a principal city.
Additional cities may qualify if they meet certain
population size and employment requirements.
Metropolitan statistical areas (MSAs) consist of a county
or counties with a minimum of one urban area with a
population of 50,000. Micropolitan statistical areas (µSAs)
consist of a county or counties with a minimum of one
urban area with a population of 10,000 and not exceeding
50,000. Some CBSAs include metropolitan divisions,
which are defined as a county or group of counties that are
delineated within a larger MSA that contains an urban core
area with a minimum population of 2.5 million people.
OMB defines Combined Statistical Areas, which are made
up of at least two adjacent CBSAs that have a defined
degree of employment interchange. Additional criteria for
these designations are provided by OMB, which establishes
nationwide standards for CBSAs.
Delineations of CBSAs are different from the various urban
and rural definitions used across the federal government.
Rural areas can exist in counties that are part of either
metropolitan statistical areas or micropolitan statistical

areas, or they can exist in counties that fall outside of such
Source: 2023 TIGER/Line® Shapefiles: Core Based Statistical Areas,
areas.
U.S. Census Bureau.
Notes: Map produced by Molly Cox, Cartographer/Geospatial
OMB intends for the delineations of CBSAs to be used
Analyst, Congressional Research Service. Some CBSAs in this map
“solely for statistical purposes.” The classification intends
expand into neighboring states.
to provide “nationally consistent delineations for collecting,
tabulating, and publishing Federal statistics for a set of
Revisions to CBSAs
geographic areas.” In practice, though, CBSAs are used for
Prior to CBSAs, the Bureau of the Budget (OMB’s
nonstatistical purposes in some federal programs (such as
predecessor) established “standard metropolitan areas,”
the Centers for Medicare & Medicaid Services’ hospital
which were first used in 1950 Census Bureau publications.
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Core Based Statistical Areas
The standards for delineating CBSAs are considered to be
nonstatistical purposes; rather, agencies may apply an
Statistical Policy Directive (SPD) No. 7 issued by OMB.
updated delineation through the notice-and-comment
CBSA revisions are conducted following the decennial
rulemaking process.
census. OMB delineates CBSAs using the most recent
decennial census data along with commuting data collected
The MAPS Act also made changes to Sections 6102 and
from the American Community Survey (ACS), which is
6309 of Title 31 of the U.S. Code as it pertains to use of
used to measure intercounty connectivity.
CBSAs in nonstatistical programs.
During the 2020 revision process, OMB requested public
OMB Bulletin No. 23-01
comment on the recommendation of raising the population
In July 2023, OMB released Bulletin No. 23-01, which
threshold to qualify a metropolitan statistical area from
reflects the 2020 standards for delineating CBSAs. The
50,000 to 100,000. After significant public opposition,
bulletin establishes the delineations, provides guidance for
OMB decided to leave the 50,000 threshold in place.
their use, and contains a list of all CBSAs. The bulletin
identifies
The 2020 standards were published on July 16, 2021, and
included a process for conducting updates to delineations
• 393 Metropolitan Statistical Areas, which contain 1,186
over a 10-year period.
counties;
Annual Updates
• 542 Micropolitan Statistical Areas, which contain 658
These updates address qualification of new metropolitan
counties;
and micropolitan statistical areas and are expected to impact
fewer counties.
• 37 Metropolitan Divisions;
Five-Year (“Mid-Decade”) Update
• 184 Combined Statistical Areas; and
This broader update addresses issues such as qualification
of various aspects of current CBSAs, titling of CBSAs, and
• 1,300 counties outside of the CBSA classification.
potential merging of adjacent CBSAs.
Through Bulletin No. 23-01, OMB reinforces that the
Decennial Delineation
delineations for CBSAs are “solely for statistical purposes.”
This is the initial redelineation following a decennial census
and adoption of revised standards; it includes the changes in
Issues for Congress
the mid-decade update and qualification of central counties.
Though CBSAs are delineated solely for statistical
purposes, their practical use in federal programs has
Relevant Statute and Legislation
attracted congressional interest. Areas of interest for
Title 44 Section 3504(e)(3) of the U.S. Code sets out
Congress may include
OMB’s responsibilities with respect to the federal statistical
system.
• what federal agencies or programs use CBSAs for
nonstatistical purposes;
In 2022, the Metropolitan Areas Protection (MAPS) Act
was signed into law (P.L. 117-219). This law provides
• how delineating CBSAs solely for statistical purposes
direction to OMB regarding revisions to CBSAs.
impacts their nonstatistical uses;
Notably, the MAPS Act changes Section 3504(e)(10) of
• how changes to CBSA delineations may impact delivery
Title 44 of the U.S. Code. Through the MAPS Act, OMB is
of services and benefits in federal programs;
required to ensure changes to CBSAs are
• instances in which laws use CBSA delineations as the
• accompanied by a public report that explains the
basis for defining other geographic areas; and
scientific basis, criteria, and methodology behind the
change and includes opinions from experts who were
• general oversight of implementation of CBSA revisions.
consulted on the change;
•
Taylor R. Knoedl, Analyst in American National
not influenced by nonstatistical considerations,
Government
including program administration or service delivery;
and
IF12704
• not used to automatically initiate an update in domestic
assistance programs that use the delineations for

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Core Based Statistical Areas

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