Probably I did not explain myself properly. I am trying to match montly IPUMS-CPS data from 1989 to 2010 (jenaury with february, with march, with april, etc.). This can be easily done from 2004 to 2010 by
collecting hrhhid and HRHHID2 from the NBER March supplement (with a sequential merge with IPUMS March file) and merging them to the IPUMS March files,
and then by applying the (modified) algorithm by Madrian, B. and L. J. Lefgren (1999)
because indeed NBER MArch Supplements contain exactly the variable hrhhid and HRHHID2.
HOWEVER, there is a problem when trying to merge the other IPUMS March Files (not comprehensive of hrhhid and HRHHID) with the NBER March supplements for the years 1989-2004. In fact for these years the NBER files have others identifiers(e.g. h_idnum, etc.), but I need always hrhhid and HRHHID2 because these are the identifiers used in IPUMS non March files. Therefore I need hrhhid and HRHHID2 to implement the match of all IPUMS monthly files
NOW MY QUESTION IS: how can I build hrhhid and HRHHID2 from the identifiers used in the NBER MArch supplement for years before 2004?
this would allow me to match all IPUMS cps monthly files available on your website
Any suggestion is apreciated