Difference between NOC and NCHILD in ACS?


I’m wondering what is the difference between NOC in ACS PUMS 2014 data which is defined as:

 NOC 2 Number of own children in household (unweighted) bb .N/A(GQ/vacant) 00 .No own children 01..19 .Number of own children in household 


And NCHILD in ACS IPUMS 2014 data which is defined as:


 NCHILD counts the number of own children (of any age or marital status) residing with each individual. NCHILD includes step-children and adopted children as well as biological children. Persons with no children present are coded "0." 


When I compare ACS PUM and IPUMS, they result in very different numbers. With ACS PUMs having a higher count of parents with children.


Specifically, I'm trying to get at parents with children and it seems that using NOC/NCHILD might be the easiest way to get a count of parents with children.


The NOC variable in the ACS PUMS is calculated via answers to question 2 on the ACS questionnaire. In IPUMS-USA, responses to question 2 can be found in the RELATE variable. One of the reasons why the IPUMS and PUMS numbers are different for this count of number of own children is that IPUMS “improves” this count by factoring in some family interelatinship nuance. Primarily, this is done by using the MOMLOC and POPLOC variables. Finally, IPUMS-USA is considering including NOC in future releases.