Joan Alker: You and your colleagues, Molly Frean and Dr. Jonathan Gruber, recently published an article in the New England Journal of Medicine titled “Disentangling the ACA’s Coverage Effects — Lessons for Policymakers,” and we understand you are releasing a new working paper that updates this study using newer data through 2015. What are the main findings of your research?  

Dr. Benjamin Sommers: We studied three policies – the mandate, Medicaid expansion, and the exchange subsidies.  Roughly 60% of the overall ACA effect on coverage that we’re able to measure is attributable to increased enrollment in Medicaid.  The remaining 40% was from the premium subsidies on the exchanges.  We found little effect of the mandate tax penalty.   We should note that there could be other ACA factors that our model can’t identify – like the effect of the exchanges making it easier to shop for coverage, or a broad impact of the mandate encouraging people to enroll (even if they weren’t subject to the tax penalty), which likely play at least some role in the decline in the uninsured rate in recent years.

Joan Alker: Can you clarify your findings about Medicaid coverage gains – how many of these folks were new enrollees? Your paper talks about early adopters — can you explain what you mean there?

Dr. Benjamin Sommers: We attempted to classify the coverage gains in Medicaid into three separate groups.  The first is the population of newly-eligible adults with incomes under 138% of the poverty level who live in the roughly 30 states that have opted to expand.  This group saw large increases in coverage – 14 percentage points on average.  The second is those adults who lived in the 6 “early expansion” states under the ACA that chose to start their Medicaid expansions in 2011-2013.  This group also saw a big upswing in coverage in 2014-2015, suggesting that the early expansions laid the groundwork for even more enrollment once the rest of the ACA kicked in.  These two groups combined for about half the overall Medicaid effect.

Joan Alker: How many people who got coverage came in as a result of the phenomenon we call the welcome mat and who are these people? Is it fair to say the majority are children and parents?

Dr. Benjamin Sommers: The other half of the ACA’s Medicaid growth in 2014-2015 was the so-called “welcome mat” group or “woodwork effect.”  These are individuals who were already eligible for Medicaid based on pre-ACA criteria, but didn’t sign up until 2014 or 2015.  Children represented a significant portion of this group, in the range of 28-45%, depending on how we analyze the data. Low-income parents were another large portion of this group. This is consistent with previous research that suggests when parents gain eligibility for Medicaid (as under the ACA’s Medicaid expansion) it produces positive spillover effects for children too –  essentially, if we cover parents, their kids come along as well.  In addition, the ACA took a lot of other proactive steps to increase enrollment among already-eligible individuals, such as streamlining the application process, creating enrollment assistance programs, eliminating asset tests for most Medicaid applicants, and the mandate.  Our findings suggest that these policies as a whole were quite successful, and there is good reason to suspect that much of these coverage gains would be at risk if the ACA were repealed.

Joan Alker: Did you find any evidence of crowd-out among Medicaid enrollees?

Dr. Benjamin Sommers: Interestingly, we find essentially no crowd-out of private insurance based on the Medicaid expansion.  This differs from much of the pre-ACA research and may reflect the complex interplay of the ACA’s many other policies.  Now, we do see that in non-expansion states, some people who would have been eligible for Medicaid instead get tax credits and sign up for exchange coverage (namely those between 100-138% of poverty).  But we see no evidence that significant numbers of new Medicaid enrollees dropped out of private insurance to sign up.

Joan Alker: Are there any other points you would like to make?

Dr. Benjamin Sommers: This is a good sign in terms of spending taxpayer dollars wisely to expand insurance.  But it’s also a sign that any kind of rollback of Medicaid eligibility would leave nearly all of these individuals without an alternative form of insurance.

Joan Alker: Thanks for sharing your expertise with our readers. We hope to hear more about your research in the future.