Michigan: ACA Medicaid expansion reaches as much as 6.4% more than total eligible

OK, YES, I know that the HHS's monthly ASPE report on ACA enrollment was finally released today. And yes, I know there's been a ton of other state-level data and other news over the past couple of days. However, as I noted on Saturday, I had to go out of town right in the middle of all of this and just got back, so I have a busy afternoon ahead of me bringing everything up to date...

So, let's start out with one of the less-obvious updates: Medicaid expansion in Michigan.

To recap: Estimates of Michigan's ACA Medicaid expansion-eligible population have ranged from 477K - 500K, thus making the enrollment data from the official state website rather eyebrow-raising:

Healthy Michigan Plan Enrollment Statistics

Beneficiaries with Healthy Michigan Plan Coverage: 507,618
(Includes beneficiaries enrolled in health plans and beneficiaries not required to enroll in a health plan.)

*Statistics as of December 29, 2014 
*Updated every Monday at 3 p.m.

Michigan has now enrolled anywhere from 1.5% - 6.4% more people in ACA Medicaid expansion than are supposedly even eligible for the program.

Again, there are three possible explanations for this overage: The estimates may have simply undercounted; the 507K figure may be a clerical error (although it's been trending above 477K for several weeks now); or it's possible that there is indeed some small amount of Medicaid fraud involved here, but likely not enough to start hyperventilating over.