The number of Americans without health insurance has been dropping dramatically in the last two years.

A new Gallup survey asking Americans if they have health insurance shows that in every state except Wyoming, the proportion of residents without health insurance has dropped since the major provisions of the Affordable Care Act — state- and federal-run insurance exchanges and an expansion of the federal Medicaid program — went into effect at the end of 2013.

But it's not an even distribution. States that have embraced the law are more likely to have seen sharp plunges in their uninsured rates. The red-leaning states of Arkansas and Kentucky, for example, either expanded the Medicaid program or brokered a deal with the federal government as a compromise. They had the two largest declines in their uninsured rates over the past two years.

Here's the percentage-point drop in the rate of people without health insurance in each state between 2013 and the first half of 2015. States that expanded Medicaid are marked with asterisks. The darker the shade, the more significant the drop:

Business Insider/Andy Kiersz, data from Gallup

Overall, the seven states with the biggest drops in their uninsured rates both expanded the federal Medicaid program and chose to run their own insurance exchanges or have a partnership with the federal government.

Meanwhile, there's only one state where more than 20% of its residents remain uninsured: Texas, where Republican presidential candidate former Gov. Rick Perry (R) has made his opposition to the law a key part of his campaign plank.

"Collectively, the uninsured rate in states that have chosen to expand Medicaid and set up their own state exchanges or partnerships in the health insurance marketplace has declined significantly more since 2013 than the rate in states that did not take these steps," Gallup's Dan Witters wrote.

"The uninsured rate declined 7.1 points in the 22 states that implemented both of these measures by Dec. 31, 2014, compared with a 5.3-point drop across the 28 states that had implemented only one or neither of these actions."

The National Center for Health Statistics also reported on Wednesday that more than 7 million people who didn't have health insurance last year gained coverage this year. About 9.2% of people of all ages, the report said, still do not have health insurance.