Those boosters include Maryland and Oregon, which ultimately enrolled just 74.5 percent and 73 percent of the people, respectively, that the Urban Institute had projected last year.
Three other Obamacare-supportive states, Minnesota, Hawaii and Massachusetts, were among the worst-performing states, enrolling, respectively, just 64.5 percent, 46.3 percent and 36.1 percent of the Congressional Budget Office's (CBO) enrollment projections.
All five of those states have had significant tech problems with their individually run Obamacare marketplaces or exchanges.
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Oregon's exchange last week voted to turn over enrollment in private Obamacare plans to the federally run HealthCare.gov exchange, after being unable to enroll anyone at all in a single online session. Maryland is scrapping its existing exchange software and plans to replace it with Connecticut's exchange model—which helped enroll 139.2 percent of the people the CBO estimated it would.
Mendelson said the problem-plagued performance of those state-run exchanges would make it unlikely that any the states that are completely reliant on HealthCare.gov would seek to build their own exchanges.
Mendelson's company, which ran an analysis based on its own projections of enrollments in each state, estimates that just 22 percent of states will actually end up beating Avalere's projections, assuming that 15 percent of enrollees don't pay their first month's premiums—a rate that is in line with what insurers have been reporting to date.
But Mendelson said that over the next five years, he expects less disparity in enrollment levels between states.
"The delivery system will drive commercial interest in Obamacare, because people who lack insurance are going to hear from their physicians, hear from hospitals, 'You should sign up,'" Mendelson said. "That's going to happen in Texas, it's going to happen in California."