The Affordable Care Act health insurance marketplaces appear set to break a record for the number of Americans enrolled, for the third year in a row.

More than 19 million people have signed up for the insurance plans often called Obamacare, and there are still three more weeks of enrollment, federal health officials said Wednesday.

On Dec. 15, HealthCare.gov – the online portal where people shop for and buy plans in most states – had 745,000 people enroll in plans. It was the biggest day for the portal since it opened a decade ago, health officials said.

"Four out of five people who are shopping are ending up getting a plan on the marketplace website for $10 or less a month in premiums," Department of Health and Human Services Secretary Xavier Becerra tells NPR. "You can't go see a movie for $10. Here's one month of health care coverage for $10 or less."

The 19 million number includes Americans who buy health insurance in state-based marketplaces like CoveredCalifornia, and people who live in the 33 states that use the federal marketplace. More than 15 million have already signed up in those states, which is about 4 million more than this time last year.

Even if you live in a state that runs its own marketplace, HealthCare.gov is a good starting place if you need to buy insurance on your own. It will direct you to your state-based exchange.

Despite the high rate of enrollment, about 25 million Americans still do not have health insurance. Becerra pointed out that it was nearly twice that number of uninsured Americans before the Affordable Care Act passed in 2010.

"If we just had about ten states that still haven't expanded their Medicaid, which they were eligible to do so under the Obamacare law, we would probably help reduce that 25 million figure substantially," Becerra says. "But there are some states that still refuse to help their citizens get on health insurance coverage through the Medicaid program."

Medicaid, the federal and state health insurance for people with low incomes, swelled to about 94 million Americans during the pandemic when states were not allowed to disenroll anyone. States have started reevaluating who should get the coverage and at least 12 million people have been kicked off the rolls so far. Some of those are losing coverage because of paperwork errors.

Some who have been kicked off Medicaid find they are eligible for good deals at healthcare.gov, but Becerra acknowledges that others are likely "falling through the cracks."

"We have to have states help us ensure that they don't disenroll people from the coverage they're entitled to under the programs we have, whether it's Medicaid or Obamacare," Becerra says.

While President Trump was in office, the number of people without health insurance ticked up as his administration limited the time enrollment was open and slashed funding to tell people about ACA insurance. Trump has said that he would repeal the ACA if elected again.