Most of the uninsured had been without coverage for two years or more, and 45 percent said they had been without coverage for at least five years, the foundation said in a report about people in the individual insurance market.

A majority of people with new health plans purchased inside and outside the exchanges rated their coverage as excellent or good and said they were generally satisfied. But four in 10 said it was difficult for them to afford their share of the premiums. And six in 10 said they were worried that insurers would raise premiums so much that they could not afford insurance in the future.

Some people who had insurance lost it because their policies did not comply with coverage standards of the Affordable Care Act. But until now, neither the government nor outside experts had reliable estimates of how many people were previously insured.