Hello, I see that the DIFFCARE and DIFFMOB variables as described in IPUMS require a condition that lasts six months or more, while the ACS removed that condition beginning in 2008. I know that you harmonize variables over time, so could you please let me know how you have done this and does it change the number that report these disabilities?
Thank you so much in advance. Vicky
You are correct that for the questions in the ACS that are used to create the variables DIFFCARE, DIFFMOB, and DIFFREM have changed over time. These changes are detailed in the comparability section of each variable. For example, the comparability section for DIFFCARE states:
Most dramatically, the 2008 ACS/PRCS dropped the stipulation that the health condition have lasted for at least six months.
In the 2008-onward ACS, there is no requirement that a causative condition has lasted at least six months. In ACS data through 2007, there is no information collected on these difficulties for people who had a causative condition for fewer than six months. These variables capture the same concepts over time, but this change in question phrasing affects comparability. Users should assume that this change in the questionnaire likely affects the number and share of individuals who report having a difficulty. I am not aware of any methods to increase the comparability of these variables over time, since the information necessary to do so is not available.
Thank you Isabel for your answer. So for clarification, you keep the 6-month wording in your documentation only for years prior to 2008 as this wording is not applicable for years since 2008. The wording does make a huge difference so this is important for users to understand.
I have one more observation. For the variable DIFFMOB, the IPUMS universe is listed as 16+ but there are actually persons who are 15 in the data. Also PUMS documentation has the universe as being 15+. Thanks for sticking with me on this. It is the first time I have really worked with disability data so it has been a learning curve.
Have a good weekend.
Vicky
Thank you for your feedback, which helps us increase the clarity of our documentation. Our documentation is intended to describe changes to the wording and universe of survey questions and variables over time. You can find original questionnaires here.
You are correct that the universe of DIFFMOB in the ACS is individuals age 15+. I have informed our IPUMS USA team of this discrepancy and they will update the DIFFMOB universe statement accordingly.