Apparently regardless of the survey sample one uses to measure Americans without health insurance, the answer will come back just about the same.

Last week, Gallup released its estimate on how far the uninsured rate had fallen over the past two years. Its survey sample indicated the percent had dropped from 18 percent in 2013 to 11.9 percent in the first quarter of 2015.

Now comes the Urban Institute’s input on the issue. In a study funded by the Robert Wood Johnson Foundation, it reported the percent of uninsured American adults 18 to 64 dropped “from 17.6 percent in September 2013 to 10.1 percent in March 2015.” In raw numbers, the uninsured declined by 15 million since September 2013, the institute said.

“Similar to earlier Urban Institute findings, states that expanded Medicaid under the ACA have seen the largest decreases in the uninsured, compared to states that opted out of the expansion,” the report stated.

Expansion states reported an average of 7.5 percent without insurance, a decline of 52.5 percent since September 2013. Non-expansion states saw a drop of 30.6 percent in those without insurance, but their uninsured rate was still about double that of expansion states.

“States that have yet to expand Medicaid should take a peek at their neighbors’ coverage gains to see what a difference expansion has made,” said Kathy Hempstead, who directs coverage issues at the Robert Wood Johnson Foundation. “All states have seen declines in the number of people without insurance, but they are far greater in expansion states, and they have impacted many groups, such as rural, urban and low-income residents, racial and ethnic minorities, and those with chronic conditions.”