IPUMS USA Variables for Metropolitan Areas

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A metropolitan area, or metro area, is a region consisting of a large urban core together with surrounding communities that have a high degree of economic and social integration with the urban core.

Since 1950, the Bureau of the Budget (later renamed the Office of Management and Budget, or OMB), has produced and continually updated standard delineations of metropolitan areas for the U.S., defining each area as a county or a set of contiguous counties, or, for New England prior to 2003, as a set of cities or towns.

IPUMS USA includes three variables that identify metro areas: METAREA, MET2013, and MET2023. This page summarizes the key differences among these variables and links to their individual geographic resource pages, which provide metro-area composition info, crosswalks between metro areas and microdata geography, and spatial match summaries.

Key Differences

Period of coverage: Each variable is available for a different set of samples. METAREA was the first IPUMS USA variable to identify metro areas and is available for the largest range of samples, but it does not extend beyond 2011. MET2013 and MET2023 are available for more recent samples but across a smaller period. We expect to extend their periods of coverage in future releases.

Variable availability by sample
Samples MET2023 MET2013 METAREA
2022-2031 ACS/PRCS (projected) X X
2012-2021 ACS/PRCS & 2010 Census X
2005-2011 ACS/PRCS & 2000 Census 5% X X
1850-1990 Censuses X

Delineation base year: METAREA uses different metro area delineations for different samples, generally following the OMB delineations in use at the time of each decennial census or, for historical samples, generating custom delineations by applying 1950 delineation rules using historical census data. METAREA also continues to use the 1999 OMB delineations for all ACS and PRCS samples through 2011. MET2013 uses only the 2013 OMB delineations, and MET2023 uses only the 2023 delineations.

In more general terms, MET2013 and MET2023 each use a single delineation across time, aiming for spatial consistency, while METAREA identifies metro areas using varying extents and coverage, aiming to reflect (approximately) real changes in population distributions and employment characteristics over time. Each approach privileges one type of comparability (spatial or conceptual) over the other.

Code scheme: METAREA uses 4-digit codes based on 1990 and 1999 OMB codes but with several adjustments to reflect historical hierarchical relationships among metro areas, aiming to maintain the first 3 digits of each code as a general identifier and using the fourth digit to distinguish smaller component metro areas. MET2013 and MET2023 codes instead use the 5-digit 2013 and 2023 OMB codes with no adjustments, making it easier to associate MET2013 and MET2023 codes with data from other sources where the OMB codes are used.

When IPUMS USA extended METAREA to 2000 samples, it was not possible in all cases to adjust the codes to reflect new 2000 hierarchies without "breaking" older codes and hierarchies, so the METAREA code system does not uniformly reflect exact hierarchical relationships across all samples. In 2003, the OMB instituted major changes in its protocols for metropolitan areas, making it significantly more difficult to extend the METAREA coding system forward. This was the primary impetus for IPUMS USA to switch to the new MET2013 and MET2023 variables for later samples.

Representativeness: METAREA identifies metro areas only for residents of areas (PUMAs or county groups) that lie entirely within a single metro area. This approach prevents errors of commission (no non-residents of a metro area are identified as residents), but it puts no limit on errors of omission (many residents of metro areas are not identified as residents). METAREA's omissions are widespread and can be very large, occasionally leaving more than half of a metro area's population unidentified, so METAREA can be poorly representative.

MET2013 and MET2023 use an alternative identification protocol that maximizes representativeness. These variables also do not identify any areas where the sum of omission and commission errors would be 15% or more, ensuring that any area identified by MET2013 or MET2023 is at least minimally well represented by corresponding microdata records.

See the variable descriptions (METAREA, MET2013, MET2023) for detailed explanations of their identification approaches.

Error reporting: METAREA's omission errors for individual metro areas are listed on the Incompletely Identified Metropolitan Areas web page. For MET2013 and MET2023, IPUMS USA provides match summary reports through the MET2013 and MET2023 resource pages and supplies separate variables, MET2013ERR and MET2023ERR, that indicate the combined omission and commission error by metro area.

County basis: For samples from 1950 through 2011, METAREA uses OMB delineations that are county-based, defining each metro area as a set of one or more contiguous counties, except in New England, where each metro area is defined as a set of cities or towns. The 2013 and 2023 delineations used by MET2013 and MET2023 are instead entirely county-based, even in New England.

Geographic Resource Pages

Visit the following resource pages to find more detailed information about the metro areas identified by each variable, including composition info, match summaries, and crosswalks.

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