About 24 percent of people who signed up online for President Barack Obama's trouble-plagued signature health care plans in 2013 were young adults, the group key to keeping the system balanced, officials said Monday.
That's a number the administration hopes to increase, the Health and Human Services officials added.
Overall, almost 2.2 million people have been able to sign up online despite a very bumpy rollout of Obama's top political legacy, HHS said in a report released Monday.
That figure comes from the start of the enrollment period on October 1 through December 28, 2013. But the report found the vast majority of enrollments—1.8 million—came in December, after a slow start.
The rollout of the website, which should allow every American without health insurance to register for coverage, has been plagued by technical problems. Obama's administration had earlier vowed to improve the site's technical failings.
Health care reform was the centerpiece of Obama's election campaign in 2008 and was passed in 2010 before being upheld in 2012 by the Supreme Court.
But Obama's popularity has nosedived to an all-time low since implementation of the Affordable Care Act, dubbed "Obamacare," got under way.
Among the people signing up, young adults aged 18-34—a key set from the insurers point of view since they are the least likely to be sick, and as such the least costly—are key to preventing cost overruns. The lower rates for younger people help the program make up costs for other ages, particularly the elderly.
"The trend so far as we released in this report are suggestive of an appropriate mix in the marketplace," said Mike Hash, Director of HHS's Office of Health Reform.
"But again to remind you, we're only halfway through the enrollment period, and we expect an increase in the proportion of young adults as we go forward."
About 79 percent of the 2.2 million received government financial help to pay their insurance premiums, the report found.
"There's no way to spin it: youth enrollment has been a bust so far," said Brendan Buck, spokesman for John Boehner, Republican speaker of the House of Representatives.
"When they see that Obamacare offers high costs for limited access to doctors—if the enrollment goes through at all—it's no surprise that young people aren't rushing to sign up," he insisted.
Explore further: For Obama, a frustrating health care rollout (Update)