The study analyzed Census Bureau data on patterns of un-insurance, and used a coverage prediction model based on the one used by the Congressional Budget Office.

The Supreme Court's decision to allow states to opt out of Medicaid expansion also contributes to Obamacare's contracted coverage. States who choose to opt out of Medicaid expansion likely will leave several million more uninsured.

But study co-author Steffie Woolhandler, a professor at City University of New York and a visiting professor of medicine at Harvard, noted that even if PPACA were fully implemented — meaning if the Supreme Court hadn't let states of the hook for Medicaid expansion — about 26 million residents still would lack coverage.

She called the law "deeply flawed."

"Many people believe that Obamacare will cover everyone. But the reform is so deeply flawed that 30 million or more will still be uninsured after it's fully implemented," she said. "We need to replace Obamacare with a simple single-payer system that would cover everyone."

Next page: Who'll be uninsured? The study estimated 80% of the uninsured under PPACA will be U.S. citizens, and most tend to be between ages 18 and 44, with a few million in younger and older age demographics.

The perception was that PPACA would cover many U.S. residents, while leaving a majority of non-residents uninsured as millions of illegal immigrants won't qualify for coverage.

Demographics of the uninsured also will change under PPACA, the study authors said.

"While blacks and Hispanics will continue to be overrepresented among the uninsured, the majority will be non-Hispanic, white, low-income, working-age adults, many of them employed," study authors wrote.

Researchers said nearly 5 million Texans and 3.7 million Californians will remain uninsured in 2016. Last month, officials at Covered California, the state agency tasked with setting up the state exchange, released health plan and sample rate information, calling the access a "home run for consumers in every region of California." The agency said that up to 5 million Californians next year will be able to shop for insurance from 13 health insurance plans.

This analysis suggested the uninsured under PPACA will be heavily low-income, even though many of those people will have access to subsidized health insurance. Despite that, some might not find it affordable. A recent survey by InsuranceQuotes.com found that more than three in five uninsured Americans say the main reason they lack health insurance right now is because they can't afford it. But those uninsured also said they don't believe PPACA will make the law any more affordable.

Experts warn that without massive participation in the exchanges, health care costs may surge because not enough healthy people will participate to offset benefits payouts. Beginning Jan. 1, uninsured Americans will be forced to pay a penalty of either $95 or 1 percent of income, whichever is greater, if they don't buy insurance. The fine increases each year.

The administration has been touting the law and rallying consumers to participate in the newly formed exchanges in the lead up to Oct. 1, the date when open enrollment begins for health plans.

In California last Friday, President Obama encouraged the uninsured or those paying high prices for health insurance to sign up for coverage under his landmark health care law.

Marketing the law has been a challenge. Despite the fact that PPACA was signed into law more than three years ago, many Americans remain confused or completely unaware of the implications of the law.

Kaiser Family Foundation's latest health tracking poll found that the share of the public that says they lack enough information to understand how the PPACA will affect their family is higher among the two groups the law is likely to benefit most — the uninsured (58%) and low-income households (56%).

That confusion may, in part, account for the high number of uninsured under PPACA the study points to. It's a problem the administration and other enrollment groups are working to alleviate with intense marketing efforts in the coming months.

As a result of increasing scrutiny over the law, the administration has admitted "glitches" and "hiccups" will be a part of the initial rollout of the law, but they have assured that PPACA will help all Americans with health care access and affordability long-term.

According to the Associated Press, the Obama administration is looking for about 7 million people to enroll through the exchanges, and 2.6 million of them need to be younger in order to keep costs down for the overall pool of enrollees, White House officials said.

Study authors noted that the estimated 30 million uninsured figured will begin to shrink gradually after 2016.

This article was originally posted at BenefitsPro.com, a sister site of Credit Union Times.