Colorado was one of eight states to see a significant decline last year in the number of people without health insurance, according to a National Health Interview Survey released Tuesday

Colorado’s uninsured rate for adults between the ages of 18 and 64 fell almost five percentage points to 8.4 percent in the first nine months of 2015. Overall, the uninsured rate in Colorado dropped from 9.5 percent in 2014 to 6.1 percent in the first nine months of 2015.

That put it among eight states with significant coverage gains, including Arizona, California, Florida and California. Each of the eight states with significant gains expanded Medicaid, except for Florida.

The federal report doesn’t offer reasons for the improved coverage numbers, but independent analysts attribute it to the Affordable Care Act, as well as the economic recovery.

For the entire U.S., the uninsured rate fell to just over 9 percent the first nine months of 2015. That’s a drop of more than 5 percent since 2013, when Obamacare expanded coverage.