This is a follow up question to my original re: merging NBER and IPUMS Jan/Feb Job Tenure data with its corresponding March supplements. I have been following the links that you shared, and it has been working well for the most part. However, for 2000 and 2002, h_idnum h_hhnum a_lineno a_sex and a_age have not been uniquely identifying observations in the NBER March dataset. So even though I can succesfully sequentially merge it (March NBER dataset) with the IPUMS March dataset, I am unable to merge that master March IPUMS/NBER dataset with the January counterpart, because the variables listed above do not uniquely identify persons. Even if I add statefip I am not able to get anywhere. To move things forward I have just been dropping the duplicate records, which has been around 400-500 for each year. But this makes me wonder if something is going amiss, and ideally I would retain as many potential matches as possible.
Thank you again for any help you can provide.
All the best,