WASHINGTON — As congressional Republicans move toward another vote on repealing the Affordable Care Act, new evidence was published Wednesday about the dramatic expansion of insurance coverage made possible by the law.

Nearly 17 million more people in the U.S. have gained health insurance since the law’s major coverage expansion began, according to a study from the Rand Corp., a Santa Monica, Calif., nonprofit research firm.

That tally takes into account 22.8 million newly insured people and 5.9 million who lost coverage in the past year and a half.

Researchers found gains across all types of insurance, including employer-provided coverage, government Medicaid programs and policies offered through state insurance marketplaces created by the law.

At the same time, the vast majority of Americans have seen no change in the source of their coverage, with 80 percent remaining in the same kind of insurance, researchers found.

“The ACA has greatly expanded health insurance coverage in the United States with little change in the source of coverage for those who were insured before the major provisions of the law took effect,” concluded the authors of the study, published online by the journal Health Affairs.

The Rand study, based on surveys of 1,589 working-age adults, is not as large as other polls. But the findings are consistent with national surveys by Gallup, as well as with data from the federal government, which have all shown a dramatic decrease in the nation’s uninsured rate since the health law’s coverage expansion began.

Importantly, Rand’s survey, which has tracked a panel of the same people since 2013, provides an early snapshot of where the coverage is expanding.

The biggest growth has been in the marketplaces created by the law, which now have about 11 million adult customers, about a third or whom were uninsured in 2013, according to the study.

Medicaid, another pillar of the health law, has seen enrollment grow by nearly 10 million adults since 2013.

The marketplaces allow Americans who do not get health benefits through an employer to shop for health plans that must meet basic standards and cannot turn away consumers, even if they are sick. And more than half the states have expanded eligibility for their Medicaid programs through federal aid made available by the health law.