The Affordable Care Acts progress in driving down the share of Americans who dont have health coverage began to backslide this year, according to survey data Gallup published Monday.

For the second consecutive quarter, the adult uninsured rate rose slightly between March and June, and stood at 11.7 percent at the end of last month, up 0.4 percentage points from the first quarter and 0.8 percentage points since the end of 2016 , the latest figures from the Gallup-Sharecare Well-Being Index show.

The uninsured rate remains significantly lower than before the Obamacare coverage expansion that began in 2014, and is down from a high of 18 percent during the third quarter of 2013.

Higher prices for the health insurance available the Affordable Care Acts exchange marketplaces like HealthCare.gov or sold directly by insurers appears to be the main culprit, as consumers opted to go without health coverage they decided they couldnt afford, said Dan Witters, research director of the Gallup-Sharecare Well-Being Index.

The ones that are going to be most at risk of falling out of the marketplace are those middle-income earners that are just outside of the range that qualifies them for subsidies, and therefore are going to be most vulnerable to the effects of the rate increases, Witters said.