The number of adults without health insurance dropped over 4 percentage points in 2014, the first year of the Affordable Care Act’s implementation, according to data released by the Centers for Disease Control and Prevention.

In its annual National Health Interview Survey, the CDC reported that the percentage of adults between 18 and 64 who lacked health insurance declined from 20.4 percent in 2013 to 16.3 percent in 2014. Just 2 percent of people under 65, though, were covered by private plans purchased on the federal health insurance exchange, HealthCare.gov, or the state exchanges.

The drop in the uninsured is the largest recorded by the CDC since the agency began conducting the survey in 1997.

According to the report, there were approximately 36 million Americans who still lacked health care coverage last year.

The number of adults between 18 and 64 years old with public coverage increased from 16.7 percent in 2013 to 17.7 percent in 2014. Among young adults between 19 and 25, public coverage increased from 16.1 percent in 2013 to 19.1 percent last year. More than 42 percent of children were on public plans in 2014.

Almost 64 percent of Americans under 65 were covered by private plans.

The report also noted that adults living in states that expanded Medicaid under Obamacare were more likely to be covered.

Drew Gonshorowski, a senior policy analyst at The Heritage Foundation, told The Daily Signal it should be noted that though the data is based on a survey, it is still considered reliable.

Gonshorowski said that while there have been gains in the number of Americans with health insurance, many are due to Medicaid expansion.

“Enrolling them in Medicaid isn’t the answer,” he said.

The CDC interviewed 111,682 people for the survey.