Questions about "not matched" observations between NBER and IPUMS CPS monthly data

[kyungmin_lee]

In order to use some variables in the NBER CPS monthly files, I am currently working on linking NBER CPS monthly to IPUMS CPS monthly data files by using (1) “hrhhid”, (2) “hrhhid2”, (3) “lineno”, (4) “year”, and (5) “month”. After linking two data sets, I found that there are “not matched” observations in both NBER and IPUMS CPS monthly files. The all “not mathced” observations in the NBER CPS monthly have pulineno=-1. But what I don’t understand is “not matched” observations in the IPUMS CPS monthly.

I read the previous question and answer in the “Why are there differences in the number of observations between IPUMS CPS and NBER data files?”

Why are there differences in the number of observations between IPUMS CPS and NBER data files?

I dowloaded the cps 2001 files through the IPUMS-CPS system and also from the NBER web page. The total number of observations in the first case is 1,712,631 while the NBER files report 1,742,243. Does these differences affect any descritive and regression analysis? Thank you.

The answer for that question was (1) oversample in IPUMS CPS and (2) non-response households in NBER CPS monthly. According to this answer, the “not matched” observations in IPUMS CPS should be oversample. But I still have concern because I downloaded only IPUMS CPS monthly samples. Is there a way to check whether “not matched” observations in IPUMS CPS monthly are over sample? Or is there any other reason for these “not matched” observations in IPUMS CPS monthly files?

Thank you.

[kyungmin_lee]

I found that I made mistakes in my coding. All observations in IPUMS CPS monthly are matched to observations in NBER CPS monthly in my sample. “Not matched” observations in NBER CPS monthly are those who did not have interview.