According to survey data from Gallup:

• The percentage of uninsured Americans peaked at 18.0% in the third quarter of 2013
• After the first enrollment period under the Affordable Care Act. the uninsured rate fell 1.5 points, from 17.1% for the fourth quarter of 2013 to 15.6% for the first quarter of 2014
• After the second enrollment period under the Affordable Care Act, the uninsured rate fell one point, from 12.9% in the fourth quarter of 2014 to to 11.9% in the first quarter of 2015

Source: "In U.S., Uninsured Rate Dips to 11.9% in First Quarter," Gallup, Inc., April 13, 2015, http://www.gallup.com/poll/182348/uninsured-rate-dips-first-quarter.aspx?utm_source=CATEGORY_HEALTHCARE&utm_medium=topic&utm_campaign=tiles