Medicare Part D

Hi I used 2018-2021 data for those age 65+ and found that only about 45% had Medicare Part D coverage. The Centers fof Medicare and Medicaid Services, 75% of the age 65+ group has Medicare Part D. Does anyone know about why there is such discrepancy? Percentages with Medicare Advantage program and private insurance coverage are consistent with the known perentages. On the data set, the variable name is: MCAREPARTD. I looked up NHIS questionnaire to see if it only refers to stand-alone Medicare Part D (that is, not including Part D through Medicare Advantage programs). If that is the case, the ~45% in each year is about right. However, the questionnaire skip patterns does not specifically mention to exclude Medicare Advantage people. Would anyone be able to shed light on this? Thanks so much.

I want to note that we have seen this request and I am looking into it, but don’t have a definitive answer at this time (but hope to have more information next week). My first suspicion is that some amount of the discrepancy is related to the target population of the two data collections. NHIS focuses on the community-dwelling population (e.g., it excludes individuals in nursing homes, which may be highly relevant for this question). Additionally, while the universe of MCAREPARTD should be restricted to those on Medicare (IPUMS NHIS variable HIMCAREE), I wonder about the focal population of CMS data versus NHIS data is also a contributing factor. I assume that there is another layer beyond this and hope to have an update next week. Thanks for your ongoing patience!

Thanks so much for your response. I will wait for your update next week. I was looking up NHIS questonnaires, and I wonder the difference is also becasue NHIS Part D question did not include those in Part C or MA-PD?
I have another question about discrepancy on Medicare Advantage (Part C). In fact, the NHIS Part C percantage is lower than the national average of Part C. The NHIS Part C question is specifically about those who have Part B and thoese who refused/did not know if they had Part B. Would you be able to shed light on this, too?