# Question about longitudinal weights

**URL:** <https://forum.ipums.org/t/question-about-longitudinal-weights/4005>\
**Category:** CPS\
**Created:** [March 2, 2021, 7:18pm UTC](https://forum.ipums.org/t/question-about-longitudinal-weights/4005 "2021-03-02T19:18:58Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![scampbell](https://avatars.discourse-cdn.com/v4/letter/s/7cd45c/32.png) [@scampbell](https://forum.ipums.org/u/scampbell)\
**Post date:** [March 2, 2021, 7:18pm UTC](https://forum.ipums.org/t/question-about-longitudinal-weights/4005/1 "2021-03-02T19:18:58Z")

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I have created a longitudinally matched dataset for month in sample 1 to month in sample 4, February to May and March to June 2020. I matched respondents based on cpsidp, sex, age, race, education, and Hispanic status. However, about ten percent of respondents have a lnkfwmis14wt value 0. Why would that be the case?

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**Author:** ![Matthew\_Bombyk](https://avatars.discourse-cdn.com/v4/letter/m/34f0e0/32.png) [@Matthew\_Bombyk](https://forum.ipums.org/u/Matthew_Bombyk)\
**Post date:** [March 5, 2021, 7:15pm UTC](https://forum.ipums.org/t/question-about-longitudinal-weights/4005/2 "2021-03-05T19:15:16Z")

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LNKFWMIS14WT is zero in these circumstances:

1. Any cases that do not have MISH = 1 (see the [Universe page](https://cps.ipums.org/cps-action/variables/LNKFWMIS14WT#universe_section) for LNKFWMIS14WT).
2. Any individual who does not appear in all of the first four months in sample. They may have a missing survey in one or more of those months, or the sample may not be available.

I suspect these are why you are seeing so many zeros, but please follow up if you think that’s not the case.

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**Author:** ![scampbell](https://avatars.discourse-cdn.com/v4/letter/s/7cd45c/32.png) [@scampbell](https://forum.ipums.org/u/scampbell)\
**Post date:** [March 8, 2021, 2:55pm UTC](https://forum.ipums.org/t/question-about-longitudinal-weights/4005/3 "2021-03-08T14:55:56Z")

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I see. So the weight would equal zero if someone answers the survey in MISH1, skips MISH2 and/or MISH3, then returns in MISH4?

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**Author:** ![Matthew\_Bombyk](https://avatars.discourse-cdn.com/v4/letter/m/34f0e0/32.png) [@Matthew\_Bombyk](https://forum.ipums.org/u/Matthew_Bombyk)\
**Post date:** [March 8, 2021, 4:29pm UTC](https://forum.ipums.org/t/question-about-longitudinal-weights/4005/4 "2021-03-08T16:29:03Z")

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That’s right.