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Codes and Frequencies

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MSASIZE reports whether the household was located inside or outside a Metropolitan Statistical Area (MSA), and, for households within MSA's, the population of the MSA (reported in intervals). An MSA is a county or group of contiguous counties that contains at least one city with 50,000 or more inhabitants or includes a Census Bureau-defined urbanized area of at least 50,000 inhabitants with a metropolitan population of at least 100,000. Information on whether the household was located within an MSA and on the size of the MSA was added by the National Center for Health Statistics, not collected from respondents.

The Codebook for the 1985 NHIS public use files notes, "The new field has been added in 1985 primarily to enable grouping MSA data by broad population density categories, since specific MSA's are no longer identified."

Related Variables 

For further discussion of the definition of MSA's, see METRO (Metropolitan residence). For years prior to 1985, a very limited number of MSA's are identified in METAREA (Metropolitan area).


The intervals used to group MSA's by population size differ between 1985-1994 and 1995-2001.


In the earlier period, MSA's were grouped into four categories: Under 100,000 inhabitants; 100,000 to 249,999 inhabitants; 250,000 to 999,999 inhabitants; and 1,000,000 or more inhabitants. In the later period, MSA's were grouped into six categories: Under 250,000 inhabitants; 250,000 to 499,999 inhabitants; 500,000 to 999,999 inhabitants; 1,000,000 to 2,499,999 inhabitants; and 5,000,000 or more inhabitants.

IPUMS NHIS uses a composite coding scheme to maximize comparability across these two periods.


The first digit identifies the three population size categories that are consistently available: "1" for "Under 250,000"; "2" for "250,000 to 999,999"; and "3" for "1,000,000 or more." The second digit of MSASIZE preserves the additional detail of categories only available for 1985-1994 and only available for 1995-2001.


  • 1985-2001: All households.


  • 1985-2001