I have a question about Minor Civil Divisions (MCDs) and the file FIPS_codes.xls mentioned in the codebook entry for the variable MCD. It says in the codebook entry that “Coding of MCD was based on a listing of codes used for the 1990 U.S. census.” However, I have looked online extensively for census county subdivision/MCD FIPS codes and have not been able to find any that correspond to the ones in FIPS_codes.xls file (including for the MCDs that exist today and are not merely historical). Does anyone know where I could find the MCD codes on which the codes in FIPS_codes.xls were based, and (ideally) a crosswalk from those codes to (present-day) FIPS codes?
After looking at the file linked from the MCD page and MCD resources based on the 1990 FIPS system, I understand your confusion. Even after accounting for the state identifiers being STATEICP values (rather than STATEFIP), the relationship between the MCD codes and FIPS system is not apparent to me.
While this doesn’t answer your question about how the codes are created or your request for a crosswalk, my best current recommendation is that you leverage the string values in the FIPS_codes.xls file from the MCD page. MCD values are only nominally integrated (i.e., we don’t account for boundary changes over time, so are only matching based on the name of MCD).
I am trying to track down information on how the coding systems relate to one another, and will report back if I find something. It seems reasonable that we will eventually map IPUMS USA and IPUMS NHGIS to allow NHGIS to produce tabulations for MCDs–but I want to be clear that there are no plans to do this currently. This work would require creating documentation on how the MCD values in IPUMS USA were created (assuming I am not able to find this). I wish I had a clearer answer for you.