At the same time, combined membership in the five insurers grew by a combined total of 23 million from 2010 to 2016, more than double the number of members added in the prior five years. Medicaid and Medicare enrollment in the five insurers grew from 12.8 million to 25.5 million.
All five insurers, which enroll a combined 125 million or so members, also continued to be profitable during the time period, noted the authors of the Health Affairs report, Cathy Schoen and Sara Collins.
The report underscored the fact that the biggest insurers have profited from Obamacare and from government-run health coverage programs even as they derive a relatively small share of their business from individual health plans sold on Obamacare exchanges.
Obamacare, starting in 2014, required nearly all Americans to have some form of health coverage or pay a tax penalty.
That coverage could be from employer-sponsored health plans, government-sponsored coverage, such as Medicare and Medicaid, military-sponsored coverage or individual health plans.
Medicare, which covers primarily older Americans and people with disabilities, is paid for out of the federal government's coffers.
Medicaid, which covers primarily low-income adults and children, is jointly funded by the federal government and by individual states.
Medicaid has provided a significant share of the gains in health coverage nationally under Obamacare, which authorized the loosening of eligibility standards.
In their report, Schoen and Collins noted that "companies with significant Medicare or Medicaid enrollment have continued to insure beneficiaries in states where the insurers do not participate in" government-run Obamacare exchanges that sell individual health plans.
The duo wrote, "Given the insurers' dependence on public programs, there is potential to improve [health coverage] access if federal or state governments, or both, required insurers that participate in Medicare or Medicaid to also participate in the [Obamacare] marketplaces in the same geographic area."