Obamacare cut the share of people in the U.S. without health insurance by two percentage points this year, the Centers for Disease Control and Prevention said in a report today.

In the first three months of 2014, 18.4 percent of adults under age 65 lacked health insurance, down from 20.4 percent last year, according to the CDC survey. The fall in the uninsured rate was helped by 3.7 million people who bought private health insurance sold under the Patient Protection and Affordable Care Act, the CDC said.

While studies by outside researchers have recorded a drop in the U.S. uninsured rate this year, the CDC survey is the first official government report to register such a decline. The 28,000-person survey didn’t count enrollment under the health law in late March and early April, when millions of coverage applications were accepted.

“Between 2013 and the first three months of 2014, there were significant decreases in the percentages of persons who were uninsured at the time of interview among persons of all ages,” according to the CDC report.

The U.S. Census will also release a report today on insurance coverage in 2013. The widely cited Census figure will serve as a baseline in 2015 for measuring expansions of insurance coverage under the Affordable Care Act.

Another study, published last month in the New England Journal of Medicine, estimated that about 10.3 million people gained insurance coverage under the health law this year.