President Barack Obama’s Affordable Care Act has pushed the country’s uninsured rate to a historic low since the law went into effect despite Republican efforts to dismantle it. “Since the passage of the Affordable Care Act almost five years ago, about 16.4 million uninsured people have gained health coverage -- the largest reduction in the uninsured in four decades," Health and Human Services Secretary Sylvia Burwell said in a statement accompanying a report released Monday on the success of the health care act popularly known as “Obamacare.”

Of the estimated 16.4 million people who gained coverage, 14.1 million adults got their insurance after the big Medicaid expansion at the end of 2013 while 2.3 million young adults got covered by being allowed to stay on a parent’s plan until the age of 26. The strong signup trends were echoed by independent studies, including the Gallup-Healthways Well-Being Index, according to the Associated Press.

All racial and ethnic groups showed gains in coverage, but the biggest improvement came among minority groups. The uninsured rate for Hispanics dropped by more than 12 percent; African-American uninsured rates fell more than 9 percent and white uninsured rates fell more than 5 percent.

Republicans, who currently control both the chambers of Congress, are still dedicated to repealing the health care act although Obama has said he is sure to veto any such legislation, according to Reuters. The House of Representatives has voted to repeal Obamacare 56 times since it passed March 23, 2010, which, besides expanding the low-income Medicaid system, established federal subsidies to make coverage more affordable and available to everyone regardless of pre-existing conditions. Conservative media and Republican figures often said Obamacare would lead to higher costs to the individual and that the health care act would lead to an increase in the number of uninsured -- claims that have been largely debunked, especially in light of Monday’s report.

However, the health care act still faces a threat from a case currently before the Supreme Court, King v. Burwell, which centers on whether the federal subsidies can legally be applied to all states. The plaintiff claims the exact wording of the law only allows subsidized coverage in states that have set up their own insurance exchanges, which would include just 13 states and the District of Columbia, and not states that rely on the federal marketplace. Independent estimates say about 9.6 million people could lose coverage if the subsidies are struck down, according to Huffington Post. A decision is expected by the end of June.