I want to look at the household income data (FTOTINC) for the 5 NYC counties from 1950 to 2019. It however seems like there is no FTOTINC data on the county level (COUNTYFIP variable) for any of these 5 counties for years 1950-1960-1970 nor 2000, but for 1980 and 1990 there is. Why is this the case? Is there another geographic variable I should be using for these years?
If you look at the codes page for COUNTYFIP, you can find which IPUMS USA samples have each county identified. It looks to me like Queens and Kings county are identified back through 1960 (but not 1950), though I haven’t checked the others. I just tabulated FTOTINC for the 1960 5% sample for King’s County (STATEFIP=36 and COUNTYFIP=47), and there were a large number of valid cases. How did you determine that those data were not available?
I’ll also note that median family income at the county level is available for the 1950 census through IPUMS NHGIS (Table NT39. Median Family Income (1949) of Families [Value ranges, county level only]), so you may be able to fill in that year using those data.