The findings are "a sign that the Affordable Care Act, commonly referred to as 'Obamacare,' appears to be accomplishing its goal of increasing the percentage of Americans with health insurance coverage," the polling firm said.
The 1.5-percentage-point drop since last quarter is the equivalent of roughly 4.7 million Americans gaining coverage. Other recent estimates have placed that figure at 9.5 million and 8.3 million. Those estimates included the 3 million young adults who gained coverage under the law prior to this year.
Gallup also detected signs of the late March enrollment surge that helped push overall Obamacare enrollment over 7 million. The uninsured rate fell more than a full percentage point from the first half of March to the second half.
Gallup's findings are based on more than 43,500 interviews with U.S. adults, conducted from Jan. 2 to March 31.