I know similiar questions have been asked, but I just want to make sure. In the COUNTY variable description page, there’s an Excel spreadsheet provides a list of counties and their corresponding ICPSR and FIPS codes available in each year from 1950 onwards. So does it mean that there’s no county-level data in IPUMS for those counties that are not in list? Thanks.
Yes, that is correct. In samples from 1950 onward, counties are not identifiable in public use microdata. In these samples, some counties are identifiable in IPUMS USA due to alternative low-level geographic identifiers. The spreadsheet you linked above summarizes which counties are identifiable in which samples. If you are looking for aggregated data at the county level, you may find the data available via IPUMS NHGIS helpful.