WASHINGTON — President Obama’s health law has led to an even greater increase in health coverage than previously estimated, according to new Gallup survey data, which suggests that about 12 million previously uninsured Americans have gained coverage since last fall.

That is millions more than Gallup found in March and suggests that as many as 4 million people have signed up for some kind of insurance in the last several weeks as the first enrollment period for the Affordable Care Act drew to a close.

Just 12.9% of adults nationally lacked coverage in the first half of April, initial data from the Gallup-Healthways Well-Being Index indicate. That’s the lowest rate since the survey began in 2008.

Eighteen percent were uninsured in the third quarter of 2013, just before Americans could start shopping for coverage on the new online marketplaces created by the law.


Gallup pollsters cautioned that the data are preliminary but said it is increasingly clear the health law is responsible for the gains. “It is fair to say it is having a significant impact,” said Dan Witters, the survey’s research director.

Critics of the law, sometimes called Obamacare, say it has done little to expand health coverage.

Gallup’s latest data, which parallel recent findings from Rand Corp. and the Urban Institute, lump together all coverage gains, including those on the marketplaces, as well as through other forms of insurance, such as Medicaid, employer-provided coverage and health plans purchased directly from insurers.

The data also take into account any losses in coverage the law may have brought about by the cancellation of health plans that did not meet new standards.


The health law enables Americans who do not get coverage through an employer to select a plan on government-run marketplaces. Insurers must offer a basic set of benefits and can no longer turn away sick customers.

Americans making less than four times the federal poverty level — about $94,000 for a family of four — qualify for government subsidies in most parts of the country.

In about half the states, very low-income Americans can sign up for Medicaid. Most Republican-led states, however, have not expanded the program to cover all low-income residents, an option provided by the health law.

The disparity between states that have embraced the health law and those fighting it is already showing up in health coverage, Gallup found.


From 2013 to the first quarter of 2014, the uninsured rate fell to 13.6% from 16.1% in the 21 states that are expanding Medicaid and are fully or partially operating their own marketplaces, rather than deferring that job to the federal government.

The uninsured rate dropped about a third as much in the states that have not fully embraced the law, to 17.9% from 18.7%, the poll found

“The gap is widening,” Witters said.

The Obama administration reported last week that 7.5 million people have signed up for coverage through the marketplaces.


Not all of these people were previously uninsured, however. Some probably had coverage through an employer. Some may have bought insurance directly from an insurance company. Others may have been on government programs, such as Medicaid.

Gallup’s polling does not clarify how many of the 7.5 million were previously uninsured, nor does the survey identify whether the newly insured got coverage on a marketplace or through other avenues, such as Medicaid or an employer.

The new data do provide some new insights into who the newly insured are, however.

They appear to be slightly younger than the population at large, with two-thirds ages 18 to 49, compared with 55% of the population at large.


And they are about as healthy as the general population, according to self-reported health status.

The newly insured also seem to reflect the nation’s deep political divide over the health law; 54% are Democrats, while just 24% are Republicans.

Frank Newport, Gallup editor in chief, said that suggests Americans’ political leanings may be influencing their decisions about whether to get health insurance. Gallup has found that although about 3 in 4 Democrats approve of the health law, just 1 in 6 Republicans do.

Gallup interviews about 14,800 adults a month nationwide for the Gallup-Healthways Well-Being Index, making it one of the largest health insurance surveys in the nation.


noam.levey@latimes.com

Twitter: @noamlevey