How is SPMNUMCHILD defined?

SPMNUMCHILD is defined in IPUMS as “the number of children in the family unit.”

It corresponds to SPM_NumKids in the raw ASEC, which also defines it as “SPM unit’s number of children.”

As SPM reports count the child poverty rate as the poverty rate for people under age 18, I assumed that would be the threshold for defining SPMNUMCHILD. However, when I counted the number of person records under age 18 per SPMFAMUNIT, it didn’t match SPMNUMCHILD. For example, SPMFAMUNIT 1096001 in the 2019 ASEC shows SPMNCHILD of 0, yet it includes CPSIDP 20190203952801 which is AGE 17.

The threshold doesn’t seem to be age 17 either. For example, SPMFAMUNIT 65001 shows SPMNCHILD = 2, yet it includes only an 11-, 17-, and 41-year-old.

If not defined by age, how is SPMNUMCHILD defined?

Hello Max,

You’re picking up a very subtle definition. Here’s the definition:

“The term “children,” as used in tables on living arrangements of children under 18, are all persons under 18 years, excluding people who maintain households, families, or subfamilies as a reference person or spouse.” (

So you’re going to need to bring in MARST and RELATE to do this correctly. 18 is the cutoff but you need to exclude householders and their spouses.

In your example, the AGE 17 in SPMFAMUNIT 1096001 is a head of household.

Hope this helps,


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