This issue brief reviews the most recent survey and administrative information available about gains in health insurance coverage since the enactment of the Affordable Care Act (ACA) in 2010. We estimate that the provisions of the ACA have resulted in gains in health insurance coverage for 20.0 million adults through early 2016 (through February 22, 2016), a 2.4 million increase since our previous estimate in September 2015. These estimated health insurance coverage gains are shared broadly across population groups. Our estimate of a net reduction of 20.0 million uninsured adults is based on data from the National Health Interview Survey and from the Gallup-Healthways Well-Being Index. Other federal and non-governmental surveys of health insurance status show similar trends over this time period.