Although that still would leave about 37 million people uninsured, it's the lowest level measured in more than 15 years.
The most dramatic change took place in comparing 2013 with the first nine months of 2014. As the health care law's major coverage expansion was taking effect, the number of uninsured people fell by 7.6 million over that time.
That's "much bigger than can possibly be explained by the economy," said Larry Levitt of the nonpartisan Kaiser Family Foundation. "The vast majority has to be due to the Affordable Care Act."
Monday was the law's fifth anniversary, and supporters and detractors again clashed over its impact.
Obama says the law in many ways is "working even better than anticipated."
House Speaker John Boehner says it amounts to a "legacy of broken promises."
The health care law offers subsidized private coverage to people who don't have access to it on the job, as well as an expanded version of Medicaid geared to low-income adults, in states accepting it.
The White House says 16 million people have gained health insurance, a considerably higher estimate than Tuesday's report from CDC's National Center for Health Statistics. The White House includes results from the law's second signup season, stretching into this year.
The CDC reports compared the first nine months of 2014 with annual statistics going back as far as 1997, from the National Health Interview Survey. Among the highlights:
— The number of uninsured dropped from 48.6 million in 2010 to 37.2 million for the period from Jan.-Sept. last year. That amounted to 11.4 million fewer uninsured since the signing of the health care law.
— In 2014, about 27 million people said they had been without coverage for more than a year.
— Some 6.8 million people were covered through the health care law's new insurance markets during July-Sept. of 2014.
— The most significant coverage gains last year came among adults ages 18-64. Nearly 40 million were uninsured in 2013. But that dropped to 32.6 million in the first nine months of 2014.
— States that moved forward with the law's Medicaid expansion saw a bigger decline in the share of their residents uninsured.
The main question hanging over the law now is a Supreme Court case in which opponents argue that its subsidies are illegal in most states. They contend that the exact wording of the law only allows subsidized coverage in states that have set up their own insurance markets. Most have not done so, relying instead on the federal HealthCare.gov.
The administration counters that the context of the law makes it clear the purpose was to expand coverage in every state. A decision is expected to be announced by late June.Suggest a correction