Even before the GOP killed Obamacare's individual mandate back in December as part of their tax-reform plan, the number of Americans going without health insurance had been rising.

And now, according to a recent study, the number of uninsured US adults between the ages of 19 and 64 climbed to 15.5% in March 2018 compared with 12.7% in 2016. That's tantamount to 4 million people losing insurance, according to CBS.

The number of uninsured adults between the ages of 19 and 64 rose to 15.5 percent in March 2018, up from 12.7 percent in 2016. An estimated 4 million people lost individual coverage during that period, while the number of people with employer-sponsored coverage stayed steady. Adults with lower incomes - about $30,000 for an individual and $61,000 for a family of four - saw a much higher increase: 25.7 percent in March 2018 compared to 20.9 percent in 2016.

Perhaps the biggest contributor to rising uninsured rates, according to the study, is the coverage gap, which leaves poor Americans in many states unable to afford health insurance. The gap first emerged in 2012, after the Supreme Court ruled that Obamacare's mandate forcing states to expand Medicaid was "unconstitutionally coercive".

The biggest increases in uninsured rates in recent years have occurred in states that did not expand Medicaid, which shouldn't come as a surprise.

Another factor may be related to the so-called coverage gap. When the ACA was passed, it mandated that all states expand their Medicaid coverage, including increasing qualifying income limits. At the same time, the ACA ruled that people whose income fell below 100 percent of the poverty level would not qualify for the ACA's government subsidies to help pay health insurance premiums. The assumption was these people would be covered by expanded Medicaid coverage, Collins explained. That plan went haywire when the Supreme Court later ruled that states were not required to expand Medicaid coverage but could do so voluntarily. As a result, people in nonexpansion states with incomes below the ACA subsidy limits often don't qualify for Medicaid. Indeed, the survey found the steepest increases in uninsured rates occurred in states that did not expand Medicaid. Collins predicted the rising uninsured trend is likely to continue. One reason: The repeal of the individual mandate, which required people to buy insurance or face penalties. The new tax law did away with that provision and eliminated penalties starting in 2019. Commonwealth found that 5 percent of people with insurance are planning to drop coverage once the mandate becomes obsolete. "That's not a huge number, but it is something," said Collins.

At least one former ACA antagonist is warning that the repeal of the individual mandate was a mistake. Tom Price, former secretary of the Department of Health and Human Services, said during a recent health-care conference in Washington that eliminating the individual mandate would almost certainly drive up premiums. Last year, the CBO forecast that 13 million people would lose coverage if the mandate was eliminated.

Of course, this trend can't continue for much longer until Obamacare experiences an all-out collapse as insurers decide that it's simply no longer worth it to offer health-care plans on the ACA's exchanges. As premiums soar, more and more people will be forced out of the market, deteriorating risk pools and forcing insurance companies to reconsider their participation.

In an interview last year, Aetna CEO Mark Bertolini warned about the impending Obamacare "death spiral", saying "it's not going to get any better; it's getting worse."