The uninsurance rate among non-elderly adults in the United States fell from 20 percent to 15 percent during the Affordable Care Act's first open-enrollment period, a survey conducted by the Commonwealth Fund finds. According to the report, Gaining Ground: Americans' Health Insurance Coverage and Access to Care After the Affordable Care Act's First Open Enrollment Period (24 pages, PDF), an estimated 9.5 million fewer adults between the ages of 19 and 64 were uninsured during the April-June 2014 period than during the July-September 2013 period. A large part of the decline was driven by young men and women obtaining coverage; indeed, the uninsurance rate among 19- to 34-year-olds fell from 28 percent to 18 percent, with an estimated 5.7 million fewer young adults uninsured. The report also found that in the states that had expanded their Medicaid programs by April, the uninsured rate for adults with incomes below the federal poverty level declined from 28 percent to 17 percent, while in states that had not expanded Medicaid, the rate remained essentially unchanged, at 36 percent.