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FAMUNIT is a 2-digit numeric variable.


FAMUNIT indicates to which family within the housing unit each person belongs. If there is only one group of related individuals, all members of the household will be coded 1; if there is a second, separate such group, all members of that family group will be coded 2, and so on. All persons with a RELATE code less than 1100 are included in FAMUNIT 1. All persons with a RELATE code of at least 1100 receive a FAMUNIT code of 2 or greater unless they are linked via birth, marriage, or adoption to someone with a RELATE code of less than 1100. This means that some households contain no persons with a FAMUNIT code of 1: for example, household fragments (identified via FRAGMNT) receive a FAMUNIT code of 2.

The Census Bureau defines "primary families" as groups of persons related to the head of household, and "primary individuals" as household heads/householders residing without kin. In the IPUMS, primary families and primary individuals are identified in FAMUNIT with a code of 1; each secondary family or secondary individual receives a higher code.

Note that FAMUNIT is an IPUMS-derived variable using IPUMS-derived family interrelationships, and does not directly correspond to the Census Bureau's enumeration of families within households. See FTYPE, FAMKIND, and FAMREL for variables that correspond to Census family units. FAMUNIT is also not analogous to the Census Bureau's concept of "related subfamily." People in "related subfamilies" as defined by the Census Bureau are necessarily related to the householder, and they will be included in FAMUNIT 1.

An Introduction to the Family Interrelationship Variables can be found on IPUMS-USA. 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 comparability of this variable is affected by the information available on family relationships. See RELATE (Relationship to household head) for discussion of variation across years.

Comparability with IPUMS-USA

FAMUNIT is conceptually identical in IPUMS-USA and IPUMS-CPS, but the comparability of this variable across the two databases is affected by the more limited detail available on relationship to household head in IPUMS-CPS.


  • All persons.


Years Jan Feb ASEC Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1962 – 1975 - - X - - - - - - - - - -
1976 – 2023 X X X X X X X X X X X X X
2024 X X - X X X - - - - - - -


This variable has no flags.

Unharmonized Variables

No variables available