Ive created a county fips variable using the county and statefip variables in order to merge the IPUMS dataset with another dataset. However, I see that there are a lot of zero values for the county variable, specifically for all of alaska as well as for certain counties in each state.
Is there documentation explaining these zero values?
the county variable description states that:
0000 = County not identifiable from public-use data (1950-onward only)
But I am wondering if you can provide more specific details about why it was not avaiable? Were the population in these counties not sampled?