# Q for Tim Moreland Re: Trouble merging NBER and IPUMS **URL:** \ **Category:** CPS\ **Created:** [December 18, 2014, 5:48pm UTC](https://forum.ipums.org/t/q-for-tim-moreland-re-trouble-merging-nber-and-ipums/747 "2014-12-18T17:48:00Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![ccrawford511](https://avatars.discourse-cdn.com/v4/letter/c/c89c15/32.png) [@ccrawford511](https://forum.ipums.org/u/ccrawford511)\ **Post date:** [December 18, 2014, 5:48pm UTC](https://forum.ipums.org/t/q-for-tim-moreland-re-trouble-merging-nber-and-ipums/747/1 "2014-12-18T17:48:00Z")
Hi Tim- 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, Caroline ---
**Author:** ![Tim\_Moreland](https://avatars.discourse-cdn.com/v4/letter/t/f1d935/32.png) [@Tim\_Moreland](https://forum.ipums.org/u/Tim_Moreland)\ **Post date:** [December 18, 2014, 8:15pm UTC](https://forum.ipums.org/t/q-for-tim-moreland-re-trouble-merging-nber-and-ipums/747/2 "2014-12-18T20:15:00Z")
Using the raw [NBER March supplement](http://www.nber.org/data/current-population-survey-data.html) dataset for 2000, I am unable to replicate your issue. I see 133,710 observations in the raw dataset, with a corresponding 133,710 unique combinations of h\_idnum, h\_hhnum, a\_lineno, a\_sex, and a\_age. I would recommend double-checking that your raw dataset is beginning with the correct number of observations to make sure there were no problems downloading the NBER dataset (see this [sample size table](https://cps.ipums.org/cps/sample_sizes.shtml)). If you are still seeing duplicates in your file, please email [ipums@umn.edu](mailto:ipums@umn.edu) with the identifier values for a couple examples of duplicates. Hope this helps. ---
**Author:** ![ccrawford511](https://avatars.discourse-cdn.com/v4/letter/c/c89c15/32.png) [@ccrawford511](https://forum.ipums.org/u/ccrawford511)\ **Post date:** [December 18, 2014, 10:03pm UTC](https://forum.ipums.org/t/q-for-tim-moreland-re-trouble-merging-nber-and-ipums/747/3 "2014-12-18T22:03:00Z")
Hi Tim– Thank you for getting back to me. I have sent an email to the IPUMS email address as you directed, but thought that I would share this more specific information with you in case it’d help. A specific example of where this is happening would be NBER’s March 2002 supplement. The variables that are supposed to uniquely identify observations (h\_idnum h\_hhnum a\_lineno a\_sex a\_age) have not been doing so. The IPUMS March 2002 dataset has the same total number of observations (217,219) as the NBER March 2002 dataset. I checked online and ensured that this is the correct March 2002 sample size. Because of the common sample size I am able to sequentially merge the March 2002 NBER dataset with the March 2002 IPUMS dataset. But this isn’t very useful as I am unable to use this newly created master March IPUMS/NBER to match with its Jan/Feb counterpart without the unique identifiers. An example of duplicate identifiers is the following from the March 2002 NBER dataset: h\_idnum (200068101345321) h\_hhnum (1) age (9) sex (male) lineno (3). I have found variables such as “h\_seq” that allow me to uniquely identify observations within the March 2002 Supplement, but this is not very useful either as h\_seq is not a variable that is shared by the Jan/Feb 2002 Supplement. Thank you again for your response and support in this process. All the best, Caroline