Slightly more than seven in 100 adult residents of states that chose to expand Medicaid currently do not have health insurance — less than half the rate of those without coverage in states that didn't expand Medicaid. 

That is one of the key findings of an Urban Institute analysis of Americans with and without health insurance. Funded by the Robert Wood Foundation, the study charted a steady and impressive decline in Americans without health coverage since 2013, a decline that was far sharper in the Medicaid expansion states. 

Overall, the Urban Institute analysis showed, the uninsured rate fell from 17.6 percent in September 2013 to 10.4 percent this past September. Among other findings: 

• Coverage rates climbed 10.1 percentage points among young adults (aged 18-30);

• Rates climbed 12.4 percentage points among Hispanics;

• Rates climbed 15.6 percentage points among adults in families with annual incomes less than 138 percent of the federal poverty level, or $27,724 for a family of three. 

"Despite the gains, individuals in these same groups remain the most likely to be uninsured, so continued enrollment efforts should be targeted at them," researchers said.