Nearly 1 million more young adults have obtained health insurance since the 2010 health-care law began requiring insurers to let adult children stay on their parents’ plans until age 26, according to government data released Wednesday.

The jump in enrollment caused the share of young adults who are uninsured to drop from 34 percent at the start of 2010 to 30 percent — or 9.1 million people — by March of this year, according to a national interview survey by the Centers for Disease Control and Prevention.

A Gallup poll also unveiled Wednesday pointed to an almost identical pattern.

Young adults remain more likely to go without health insurance than any other age group.

Still, after the recent stream of dismal poverty and unemployment statistics, Secretary of Health and Human Services Kathleen Sebelius welcomed Wednesday’s findings as “a really great achievement.”

“The economic downturn has taken a toll on employment among young adults,” Sebelius said during a conference call with news media. “In the past, that would have led to even more young people without health insurance. Instead, thanks to the [new law], the number of young adults with coverage has actually gone up.”

Technically, neither data source directly addresses how much of this change was a result of the new health-care rule. However, administration officials noted that the insurance rate for all other age groups remained essentially unchanged during the same period and that the trend line for young adults closely tracks the timing of the new rule’s phase-in.

At the administration’s urging, dozens of plans began voluntarily opening their rolls to young adults in the late spring of 2010, months before the official start date. All plans were required to comply beginning with their next renewal date after Sept. 23 of 2010. For many that meant last January, although some did not renew until later.

Based on the administration’s earlier estimate of the range of uninsured young adults whose parents had private coverage to which they could be added as dependents, anywhere from one-half to one-fourth of eligible young people are now signed on.

Whatever the case, the relatively small number of young adults involved, and the large share likely to be in good health compared with older adults, means any reduction in the cost of caring for the uninsured will probably be limited, analysts said.

For similar reasons, premiums are also unlikely to be substantially affected.

But Sebelius noted that there could be a larger economic benefit.

“As they begin their careers, these young adults will be free to make career choices based on what they want to do, not on where they can get health insurance,” she said.

For Luis Silva,the provision means having peace of mind as he pursues a law degree. The 23-year-old University of South Florida senior said he would have been forced to go without insurance if the law had not enabled him to keep coverage through his mother, a bank worker.

“Money is really tight,” he said. “I’m putting myself through college, already working a part-time job, literally living on ramen. . . . If it was anything more than $20 a month, I would not be able to afford it.”

That was a scary prospect for Silva, whose father owes $50,000 in medical bills he incurred after getting into a trucking accident while uninsured.

“I definitely know what can happen if you don’t have insurance. . . . This law has made a big difference for me,” Silva said.

Polls have indicated that the young adults provision is nearly as popular with Americans as a whole. But overall, public opinion of the law has remained roughly evenly divided since the law’s adoption.

For one thing, given the complex, multi-pronged nature of the health-care overhaul, “we don’t know for sure that the people who benefited from the young-adults provision know that they got that benefit” from the law, said Drew Altman, president of the nonpartisan Kaiser Family Foundation.

Polls by the foundation have revealed widespread lack of knowledge about the specific provisions in the law even among those directly impacted, he noted.

Altman predicted that once the law is fully implemented in 2014, Americans will begin moving beyond a more abstract, ideologically-based assessment to one founded on how it actually performs in practice.

But even then, “the challenge for the administration and advocates of health reform will be to make sure that when people get these benefits they know it was the [law] that delivered it to them.”