WASHINGTON -- Nearly half of the 8 million Americans who signed up for marketplace health insurance did so in the final seven weeks of the six-month enrollment period that ended April 19, the Obama administration reported Thursday.
Enrollment doubled since March 1 in 17 states, including Georgia, Texas, Florida, Louisiana, Mississippi, Missouri and South Carolina.
The late scramble for coverage netted 3.8 million new enrollees nationwide in March and April, including nearly 1.2 million young adults ages 18 to 34, who accounted for 31 percent of the final enrollment surge. In the past seven weeks, those young adults more than doubled their national enrollment totals from the prior five months.
Overall, the coveted young adult population accounted for 28 percent of state and federal marketplace sign-ups. That's short of the 40 percent the Obama administration initially sought, but it is likely strong enough to prevent a "death spiral," in which premiums would rise next year because of a lack of young health plan members.
As higher rates make insurance less affordable, some have feared that even more young people would forgo coverage, until the market ultimately implodes.
"We believe, based on the data that we've seen and independent data that's out there, that premiums will be stable, and that the risk pool [of policyholders] is sufficiently large and varied," said Michael Hash, director of health overhaul at the U.S. Department of Health and Human Services.
Young adults are important because they typically require less medical care, making them cheaper to insure. The resulting savings are needed to offset coverage costs for older plan members, generally sicker and more costly to cover. If young people don't enroll in sufficient numbers, premium revenues in the individual insurance market won't cover the cost of medical care.
But individual insurance premiums are based on a statewide risk pool that includes coverage bought both inside and outside the marketplace. Enrollment data on the estimated 5 million people who bought non-marketplace coverage haven't been reported, so it's unclear how those enrollees will affect premiums in 2015.
The true determinant of premium costs will be the health status of new plan members, which won't be known until they start seeking medical care. Insurers will submit 2015 premium rate proposals in the next few months, despite having only one to five months of claims data on new marketplace enrollees.
Before the new enrollment figures were released, the Republican-controlled House Energy and Commerce Committee produced a survey of 160 insurers suggesting that only 67 percent of federal marketplace enrollees had paid their first month's premium. But more than 300 firms are selling plans on the federal marketplace, and many insurance executives have said 80 percent to 90 percent of new plan members have paid.
White House spokesman Jay Carney called the GOP report "partial information packaged in a way to try to undermine what must be a depressing reality to those who want to repeal the Affordable Care Act."
In Pennsylvania, 318,077 people have signed up for health plans through the federal marketplace since Oct. 1. About 30 percent of Pennsylvania's enrollees are ages 18 to 34 -- a slightly larger share than the national rate -- while 39 percent are 35 to 54, and 31 percent are 55 to 64.
Women enrollees in Pennsylvania, as nationally, outpaced men, 54 percent to 46 percent.
More than 131,000 of Pennsylvania's 318,077 federal marketplace enrollees are Highmark customers, the insurer said in a news release. About 1,926 bought UPMC Health Plan coverage.
Post-Gazette staff writer Bill Toland contributed.