Just 24 percent of Americans signing up for coverage under President Obama‘s health care law through December were part of the young adult demographic, the Department of Health and Human Services announced Monday — well below the nearly 39 percent the White House had once deemed essential to the law’s success.

In a new report, HHS said that through Dec. 28 (about halfway through the six-month open enrollment period), roughly 2.2 million Americans signed up for coverage on one of the law’s health insurance exchanges. That’s well below the administration’s target of 3.3 million. And HHS still hasn’t disclosed how many of those who have signed up for insurance have actually paid their first premiums, which is necessary for enrollment to be finalized.