The percentage of adults without health insurance coverage rose 1.3 percent in 2017, from a record low during the previous year, a new Gallup poll shows. Last year’s rise marked the largest single-year increase since Gallup began tracking the statistic in 2008.

The uninsured rate rose to 12.2 percent in the fourth quarter of 2017 compared to 10.9 percent in 2016, according to the survey. That translates to an additional 3.2 million Americans who became uninsured last year.

The increase comes after Republicans in Congress effectively repealed the requirement under the 2010 health care law that most Americans have health insurance coverage. The repeal, which was in a tax bill that cleared in December, takes effect Jan. 1, 2019.

The uninsured rate had shrunk steadily after the main coverage expansions under the health law took effect in 2014, down from a high of 18 percent, according to the Gallup poll in 2013.

Gallup analysts attributed the jump to some insurance companies’ decisions to stop offering policies through the marketplaces, as well as an increase in the cost of policies that may have led some consumers to forego coverage.

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“By far, the biggest change in 2017 was the decline in the percentage of Americans purchasing their own plans, likely through ACA healthcare exchanges,” the analysts wrote.

Additionally, GOP efforts to overhaul the health law throughout 2017 may have led to confusion among consumers, they said.

While 20.3 percent of Americans said they purchased a health insurance plan themselves, likely through the federal or state marketplaces, in the last quarter of 2017, that compares to 21.3 percent who said so in late 2016.

But statistics of consumers who got health insurance coverage through other means, such as through an employer or the government, remained relatively unchanged, the report says.

The uninsured rate increased among all age groups except for adults older than 65 who qualify for Medicare. The rate for the critical 18-25 age group, considered the “young invincibles,” whose participation in the marketplace is considered important to bring healthy people into the pool and drive down premium costs, increased by two percentage points in 2017. That’s more than the increase among adults aged 26-34 and 35-64.

More black and Hispanic adults became uninsured than white adults, with the uninsured rate among black adults increasing 2.3 percentage points and the uninsured rate among Hispanic adults increasing 2.2 percentage points, compared to the uninsured rate among white adults increasing 0.7 percentage points.

More lower-income Americans joined the ranks of the uninsured, increasing 2 percentage points, compared to middle-and-high-income adults, which increased by 1.4 percentage points and 0.8 percentage points, respectively.

The uninsured rate is likely to keep rising after the repeal of the mandate next year, the analysts say.

“Without this requirement to have health insurance, it is likely that some Americans will drop their coverage,” they write. “Rising insurance premiums, which are expected to continue to increase, could also result in some Americans forgoing health coverage.”