An estimated 28.5 million U.S. residents lacked health insurance in the first six months of 2015, 16.3 million fewer than in 2013, according to a new report by the Centers for Disease Control and Prevention. The proportion of residents who were uninsured when interviewed for the National Health Interview Survey fell 5.4 percentage points since 2013, to 9%. The uninsured rate for adults under age 65 fell 8.2 percentage points in Medicaid expansion states, compared with 6.2 percentage points in non-expansion states. The report also includes estimates by Health Insurance Marketplace type and for various demographic groups. Several Affordable Care Act provisions took effect in 2014, including the expansion of Medicaid eligibility and the launch of the Health Insurance Marketplaces.