# What's the difference between serial and CPSID?

**URL:** <https://forum.ipums.org/t/whats-the-difference-between-serial-and-cpsid/1459>\
**Category:** CPS\
**Created:** [October 26, 2016, 5:52pm UTC](https://forum.ipums.org/t/whats-the-difference-between-serial-and-cpsid/1459 "2016-10-26T17:52:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Cassie](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cassie](https://forum.ipums.org/u/Cassie)\
**Post date:** [October 26, 2016, 5:52pm UTC](https://forum.ipums.org/t/whats-the-difference-between-serial-and-cpsid/1459/1 "2016-10-26T17:52:00Z")

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What’s the difference between the below two methods:

1.use year, month, serial to identify and match household

2.use CPSID to identify and match household.

Thanks much!

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**Author:** ![JeffBloem](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.ipums.org/jeffbloem/32/40_2.png) [@JeffBloem](https://forum.ipums.org/u/JeffBloem)\
**Post date:** [October 27, 2016, 3:01pm UTC](https://forum.ipums.org/t/whats-the-difference-between-serial-and-cpsid/1459/2 "2016-10-27T15:01:00Z")

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The difference primarily rests between within-sample and across-sample uniqueness. The combination of YEAR, MONTH, and [SERIAL](https://cps.ipums.org/cps-action/variables/SERIAL#description_section)provides a within-sample unique ID for each household.The [CPSID](https://cps.ipums.org/cps-action/variables/CPSID#description_section) variable, on the other hand, provides an ID that uniquely identifies households across CPS basic monthly samples. More detailed documentation about the creation and use of the CPSID variable is available [here](https://cps.ipums.org/cps/resources/linking/drew_flood_warren_2014_jesm.pdf).