# longitudinal identifiers after 2000

**URL:** <https://forum.ipums.org/t/longitudinal-identifiers-after-2000/541>\
**Category:** CPS\
**Created:** [May 31, 2014, 11:59pm UTC](https://forum.ipums.org/t/longitudinal-identifiers-after-2000/541 "2014-05-31T23:59:00Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![emilia\_sol](https://avatars.discourse-cdn.com/v4/letter/e/b19c9b/32.png) [@emilia\_sol](https://forum.ipums.org/u/emilia_sol)\
**Post date:** [May 31, 2014, 11:59pm UTC](https://forum.ipums.org/t/longitudinal-identifiers-after-2000/541/1 "2014-05-31T23:59:00Z")

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hI,

can I match individuals in IPUM-CPS OR IPUM-ACS across waves after 2000? Or maybe across waves of IPUMS-USA (ACS)? NBER only does it (for CPS) till 1998

Thanks!

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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:** [June 2, 2014, 5:22pm UTC](https://forum.ipums.org/t/longitudinal-identifiers-after-2000/541/2 "2014-06-02T17:22:00Z")

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It is not possible to track people across time using the ACS. Since the ACS was not designed to track households across time the way the CPS was, there are no identifiers created for this purpose. Furthermore, once a household is included in an ACS sample it is not allowed to be sampled again for five years.

The methods NBER uses for linking March Samples across years can be applied to beyond 1998 since the survey has not undergone a major restructuring since 1994. See [this answer](https://forum.ipums.org/t/how-do-you-link-join-a-tobacco-supplement-from-jan-to-a-march-sample-with-income-data/446/1) for more information on using this method with IPUMS-CPS data.

I hope this helps.

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**Author:** ![emilia\_sol](https://avatars.discourse-cdn.com/v4/letter/e/b19c9b/32.png) [@emilia\_sol](https://forum.ipums.org/u/emilia_sol)\
**Post date:** [June 2, 2014, 7:41pm UTC](https://forum.ipums.org/t/longitudinal-identifiers-after-2000/541/3 "2014-06-02T19:41:00Z")

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But in the NBER data extracts for years 2000-2007 (the ones I tred to use so far) the variable MIS, which is crucial for the NBER matching algorithm, is not included… what are the right datasets to download? there are so many sources, it is pretty confusing

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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:** [June 3, 2014, 2:48pm UTC](https://forum.ipums.org/t/longitudinal-identifiers-after-2000/541/4 "2014-06-03T14:48:00Z")

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In the [NBER created](http://www.nber.org/data/cps_progs.html) Stata .do and .dct files, the variable MIS (Month In Sample) is named h\_mis.

I hope this helps.