# Matching individuals on a monthly base and avoiding discontinuity in 2004

**URL:** <https://forum.ipums.org/t/matching-individuals-on-a-monthly-base-and-avoiding-discontinuity-in-2004/1408>\
**Category:** CPS\
**Created:** [September 14, 2016, 10:09am UTC](https://forum.ipums.org/t/matching-individuals-on-a-monthly-base-and-avoiding-discontinuity-in-2004/1408 "2016-09-14T10:09:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![anroe](https://avatars.discourse-cdn.com/v4/letter/a/4bbf92/32.png) [@anroe](https://forum.ipums.org/u/anroe)\
**Post date:** [September 14, 2016, 10:09am UTC](https://forum.ipums.org/t/matching-individuals-on-a-monthly-base-and-avoiding-discontinuity-in-2004/1408/1 "2016-09-14T10:09:00Z")

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In 2014 it was not possible to link IPUMS-CPS across samples ([How do you link/join a tobacco supplement from Jan to a march sample with income data?](https://forum.ipums.org/t/how-do-you-link-join-a-tobacco-supplement-from-jan-to-a-march-sample-with-income-data/446/1)). My question is whether this is possible today.

I know it is possible to identify individuals using HRHHID and HHRID2, linea, age, sex and race. At the moment I am facing a discontinuity in 2004 (from April to May) using these variables. This might due to the variables HRHHID and HRHHID2 but I do not know why.

Evaluating the descriptions of HRHHID and HHRID2, I firstly thought it might be possible to only use HRHHID2 since it was additionally backwards created from 1994-May 2004, but then the description of HRHHID says that one need both, HRHHID and HRHHID2.

So the question is how is it possible to link individuals between 1999-2013 and which variables do I have to use to uniquely identify the individuals? The goal is to match these individuals later on a yearly based month-to-month match, meaning from Jan 1999 to Jan 2000, Jan 2000 to Jan 2001…, Feb 1999 to Feb 2000 and so on.

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**Author:** ![grover](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.ipums.org/grover/32/5_2.png) [@grover](https://forum.ipums.org/u/grover)\
**Post date:** [September 16, 2016, 1:35pm UTC](https://forum.ipums.org/t/matching-individuals-on-a-monthly-base-and-avoiding-discontinuity-in-2004/1408/2 "2016-09-16T13:35:00Z")

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The linking variable for CPS is now available (see [CPSIDP](https://cps.ipums.org/cps-action/variables/cpsidp#description_section) and [CPSID](https://cps.ipums.org/cps-action/variables/cpsid#description_section)). I also recommend looking through the [Drew, Flood, Warren (2014) paper](https://cps.ipums.org/cps/resources/linking/drew_flood_warren_2014_jesm.pdf) linked in those variable descriptions as it goes into detail about some of the difficulties associated with creating these linking keys.

I hope this helps!