The wealth index for the Pakistan 1990-91 survey is available in another file. The Stata version is PKWI21DT.ZIP. Please login to your account to download that file (or the SPSS: PKWI21SV.ZIP or SAS: PKWI21SD.ZIP). I can help with the merge commands in Stata, but not in SPSS or SAS, except to say that whhid in this file matches with hhid in the HR and PR files, wlthind5 is the usual hv270 or v190, and wlthindf is the usual hv271 or v191. hv270 and hv271 in the household file are the same as v190 and v191 in the IR/BR/KR files, and the same as mv190 and mv191 in the MR file.

Everyone in the same household has the same value of the wealth index. It's defined at the level of the household, using household assets. That is, it is determined by hhid or the combination of hv001 and hv002 in the household data or v001 and v002 for the woman. Beyond saying that, I don't know how to answer your question about knowing whether you have the right value of the wealth index.

The last birth is the one with bidx=1.

If you are trying to match with Stat Compiler, you must tell me exactly what number you are trying to match, and what you get instead. However, I can only help with Stata. If you are trying to match with SPSS or SAS, someone else will have to help.