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The 1970 natality detail file does not have FIPS codes to identify states and counties. It has NCHS codes. Is there a crosswalk between the two?
I am not aware of a crosswalk. There is an appendix to the 1970 file that provides the counties associated with each code:
If you are interested in just a few counties, you can look up the FIPS codes for those counties from this source:
Another source is a list of FIPS codes by states:
However, if you are interested in converting all the NCHS codes to FIPS codes, here is some SAS code that does this:
Note that the simple algorithm of
FIPS = (NCHS*2) - 1
works for many states as FIPS codes generally follow a pattern of 1, 3, 5, 7 and NCHS codes generally follow this sequence: 1, 2, 3, 4 . . . However, there are many exceptions so the code ends up being about 50 lines long rather than 1 line. The majority of the exceptions are in New York state and Virginia.
There have been changes in FIPS county codes over time. Some counties have been renamed (Dade, Florida to Miami-Dade, Florida), which means a change in FIPS codes from 025 to 086. New counties have been formed (e.g., Broomfield county, Colorado). Thus, depending on what you are trying to do, you may need to be aware of changes in county boundaries over time. The following is a list of significant county changes since 1970 by decade: