South Carolina, and other states that aren't embracing Obamacare, have seen a smaller reduction in the percentage of uninsured residents than states that have expanded Medicaid and set up their own insurance exchanges, a new Gallup survey found.

South Carolina is among 24 states that decided against expanding its Medicaid program under the Affordable Care Act. Leaders here also chose not to create a state-based health insurance exchange, instead opting into the federal marketplace.

"The uninsured rate, on average, declined 2.5 percentage points in the 21 states (plus the District of Columbia) that have implemented both of these measures, compared with a 0.8-point drop across the 29 states that have taken only one or neither of these actions," a Gallup report on the new survey explained. The results were released Wednesday.

Nearly 19 percent of adults in South Carolina were uninsured in 2013, according to the survey.

Frank Knapp, president of the S.C. Small Business Chamber of Commerce, said the results aren't surprising.

"States that expanded Medicaid - of course they're doing much better," said Knapp, who supports the Affordable Care Act. "They have public officials saying good things and they're promoting it . Advertising and marketing works. We've seen none of it except negative marketing and negative advertising here."

Gov. Nikki Haley and S.C. Medicaid Director Tony Keck have repeatedly defended their decisions to reject Medicaid expansion and to opt out of building a state-based insurance exchange.

The S.C. Department of Insurance reported last week that nearly 100,000 residents in this state signed up for health insurance through the federal exchange during the first Affordable Care Act open enrollment period. It is not clear how many of those shoppers were previously uninsured.

Across the country, more than 7 million people have signed up for health insurance under Obamacare. Enrollment for 2015 health insurance plans begins in November. Enrollment for 2014 plans is now closed.

Reach Lauren Sausser at 937-5598.