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Person number of second father (from programming)


00 = No second father of this person in the household.


POPLOC2 is a constructed variable that indicates whether the person has two fathers who live in the same household and, if so, gives the person number of the second father (PERNUM). This variable is only non-zero when the parents identified for a child are both men. The method by which probable child-father links are identified is described in POP2RULE.

POPLOC2 makes it easy for researchers to link the characteristics of children and their (probable) fathers.

If the person identified with POPLOC2 has a spouse or partner identified through SPLOC, the spouse or partner will also be identified as a parent through POPLOC. POPRULE will communicate the method through which those relationships are identified.

In 2016, the family interrelationship variables for all samples were revised to increase comparability across IPUMS projects and include same-sex couples. Many researchers who are familiar with the previous version of family interrelationship variables will find it useful to read a brief overview of the key differences of the New IPUMS Family Interrelationship Variables. On this page you'll find information on how family interrelationship variables are constructed, common uses of these variables, and specific examples of how these variables can be used efficiently.

The pre-2016 version of MOMLOC and other IPUMS pointer variables are available here.


Due to variation in the information available for linking fathers and children, there are some differences across years. For example, in 1988 and before, the non-ASEC samples did not have a "child" value on RELATE. In these samples, "other relatives" who are under 22 are allowed to link to both "Other relatives" and to the "Head" or the "Spouse" as a father when the age difference is appropriate.

Comparability with IPUMS-USA

The development of new family interrelationship variables was prompted by the desire to have more comparability between different IPUMS projects and over time. The family interrelationship variables use common logic across IPUMS CPS, IHIS, and USA (modern years). Each project has different allowed links because of different level of detail in each project, but the logic of assigning parents in ambiguous situations is the same.


  • All persons.


Years Jan Feb ASEC Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1968 – 1975 - - X - - - - - - - - - -
1976 – 2023 X X X X X X X X X X X X X
2024 X X - X X - - - - - - - -


This variable has no flags.

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