The primary health insurance coverage reforms of the Affordable Care Act began to take effect on January 1, 2014. Between 2013 and 2016, the most recent year of American Community Survey data available, the share of Americans ages 64 and younger without health insurance fell from 17.0 percent to 10.0 percent, meaning 18.5 million more Americans with health insurance coverage. These gains in coverage were broadly distributed across all demographic, socioeconomic, and geographic groups studied.