President Barack Obama signed the Patient Protection and Affordable Care Act (ACA) on March 23, 2010, and open enrollment for all Americans began on October 1, 2013. While the ultimate outcome of the ACA, also known as Obamacare, remains to be seen, the number of people with health insurance increased in every state since the law was enacted.

In 2012, the last year before open enrollment through the ACA began, 45.6 million people nationwide, or 14.8% of Americans did not have health insurance. 24/7 Wall St. estimated that 28.6 million people, or 9.1% of Americans did not have health insurance as of March this year — a decrease of roughly 17 million people or a drop of 5.7 percentage points. Based on the change in the rate of the uninsured population from 2012 through the first part of this year, the percentage of Kentucky’s population without health insurance declined by 10.4 percentage points, the largest improvement nationwide. Iowa, on the other end of the spectrum, had the most modest improvement, with its uninsured population shrinking by 1.7 percentage points.

Click here to see how Obamacare increased health care coverage in each state. 

The 50 states used different methods to implement the ACA. Some developed their own health insurance exchanges, while others let the U.S. government facilitate enrollment. Even within those camps, each state’s health care marketplace often had unique features. One key aspect of the legislation — the expansion of Medicaid to include those making up to 138% the federal poverty level — was optional for states. More than half of all states opted to expand Medicaid coverage, including all the states that developed their own exchanges.

According to Louise Sheiner, senior fellow and policy director of the Hutchins Center on Fiscal and Monetary Policy at the Brookings Institution, political reasons are perhaps the only explanation for not expanding Medicaid. If states choose to expand the program, the federal government would pay 100% of the costs, and over time this subsidy would decrease to 90%.

Sheiner explained that there is a coverage gap between the health insurance exchanges and Medicaid — people who are too poor to get subsidies through the exchanges but not poor enough to qualify for Medicaid fall into that gap. Most of the increase in health coverage nationwide was among low-income Americans newly eligible under the expanded Medicaid program. In the 30 states that adopted the expansion, 9.5 million people have qualified for Medicaid since the ACA rollout.

While the option to expand Medicaid is aimed at helping low-income people, states opting out often had lower median household incomes and higher poverty rates. Many people purchase health insurance in order to avoid financial catastrophe, and while low-income individuals are often among those who need health insurance the most, they are also frequently unable to afford it without help. In fact, according to several studies, unpaid medical bills are the leading cause of bankruptcy in the United States.

While the Medicaid expansion provision in Obamacare is perhaps very generous to state budgets, the act is not without its critics. For example, many conservatives consider Obamacare an overreach of government that will drive up costs and result in higher taxes. In particular, ACA opponents like House Speaker John Boehner have strongly objected to the employer mandate, a provision which levies a penalty on some employers who do not offer health insurance to their employees.

The ACA’s funding mechanism has also been criticized and remains hotly debated. In a 2010 paper, Marshall Auerback, a senior fellow at the Levy Economics Institute, predicted that more people would get insurance under Obamacare. However, Auerback questioned whether more health care would get paid for in a system funded by private insurance companies. He wrote, “any real reform which cuts costs would be far less profitable.”

Nonetheless, health insurance coverage rates have gone up. Sheiner noted it is no surprise that insurance coverage rates have gone up. “When you give people subsidized insurance and make them get it, then you’re going to get more people insured.”

For Amanda Kowalski, associate professor of economics at Yale University, the hope is that reducing the share of the uninsured population will improve health outcomes and ultimately lower health care costs. Kowalski’s research on the ACA’s early adoption argues that this has happened to some extent already. States that developed their own exchanges, for example, were able to sign up more residents, thus increasing coverage and lowering costs as a result.

This is how the Affordable Care Act was implemented in each state.

Click here to see our full methodology.

1. Iowa
> Ppt change in uninsured rate, 2012-2015: -1.7
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 8.4% (5th lowest)
> Pct. population without health insurance, 2015: 6.7% (20th lowest)

More than 250,000 Iowa residents did not have health insurance in 2012, or 8.4% of the state’s population. As of March 2015, since the ACA was implemented, that percentage had dropped by 1.7 percentage points, the smallest drop in the country. In contrast, the percentage of Americans without health insurance fell by 5.7 percentage points over that period.

In many ways, Iowa was proactive in implementing the ACA. In 2012, Governor Terry Branstad wrote the U.S. Secretary of Health and Human Services at the time, Kathleen Sebelius, to make it clear that Iowa would pursue its own exchange despite some remaining questions and ambiguities surrounding the law. Additionally, the Iowa Department of Health established an interagency planning group between the departments of Public Health, Human Services, Revenue, and the Iowa Insurance Division to ensure a smooth implementation of the new healthcare law.

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2. Hawaii
> Ppt change in uninsured rate, 2012-2015: -2.2
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 6.9% (3rd lowest)
> Pct. population without health insurance, 2015: 4.7% (5th lowest)

After open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased. The improvement in Hawaii was relatively modest, likely because of the state’s already high insured rate. Hawaii enacted laws to create a near-universal health care coverage system in 1974, the first state in the nation to do so.

The percentage of Hawaii’s population without health insurance decreased by 2.2 percentage points from 6.9% in 2012 to 4.7% in March of this year, the second smallest decrease nationwide. Over the three-year period, an estimated 28,700 Hawaiians have obtained coverage. Hawaii is one of many states with a state run health insurance exchange, Hawaii Health Connector.

3. Connecticut
> Ppt change in uninsured rate, 2012-2015: -2.3
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 9.1% (8th lowest)
> Pct. population without health insurance, 2015: 6.8% (21st lowest)

There were 321,972 Connecticut residents living without health insurance in 2012, or 9.1% of the state’s population — the eighth lowest uninsured share at that time. As of March 2015, since the Affordable Care Act was implemented, that percentage had dropped by 2.3 percentage points to 6.8%, the 21st lowest uninsured rate. However, Connecticut was one of just two states where the number of residents who qualified for health insurance under the Medicaid expansion was not available. If new Medicaid recipients were factored in, the improvement would have been larger.

Connecticut was also one of eight states to accept responsibility for implementing its own exchange program and expanding Medicaid. Partially due to the state’s early implementation, Connecticut received more than $200 million in federal grants.

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4. South Dakota
> Ppt change in uninsured rate, 2012-2015: -2.4
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 11.5% (19th lowest)
> Pct. population without health insurance, 2015: 9.1% (20th highest)

An estimated 11.5% of South Dakota residents did not have health insurance in 2012, a smaller share compared to the national share of 14.8% at that time. By March this year, the percentage had fallen by 2.4 percentage points. The improvement was far lower than the nationwide decline in the uninsured rate of 5.7 percentage points. Now, 8.6% of South Dakotans do not have health insurance, inline with the nationwide share of the uninsured population.

Governor Dennis Daugaard announced in 2012 that South Dakota would not manage its own exchange program. Uninsured residents need to go to the federal exchange site in order to purchase health insurance.

5. Alaska
> Ppt change in uninsured rate, 2012-2015: -2.7
> Expanded Medicaid?: Yes
> Pct. population without health insurance, 2012: 20.5% (3rd highest)
> Pct. population without health insurance, 2015: 17.8% (the highest)

Alaska was one of just four states where the 2012 share of the uninsured population, at 20.5%, exceeded the 20%. By March this year, the percentage of the uninsured residents had fallen by 2.7 percentage points, less than half of the 5.7 percentage point decrease nationwide.

Due to the findings of a state-run study on health insurance exchange planning, Governor Sean Parnell said that Alaska would not establish its own insurance marketplace. Uninsured Alaskans need to go to the federal exchange in order to enroll. While Alaska also did not initially accept the federal offer to expand Medicaid, Parnell recently notified the legislature he will accept the funds. Alaska had the highest average health insurance premium for a 40-year old non-smoker, at $475 a month.

6. Nebraska
> Ppt change in uninsured rate, 2012-2015: -2.9
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 11.3% (16th lowest)
> Pct. population without health insurance, 2015: 8.4% (23rd highest)

Three years ago, 11.3% of Nebraska residents did not have health insurance, the 16th lowest rate of uninsured population in the country. The rate improved during the open enrollment period, and today 8.4% of Nebraska’s population is without insurance, one of the lower rates in the country. Despite having strong participation in the system, out-of-pocket costs for those opting in are relatively high. The average premium for a 40-year-old, nonsmoking man was $261, the 17th highest cost in the country.

Nebraska was one of a minority of states not to take advantage of federal incentives to expand Medicaid coverage. According to the HHS, had Nebraska expanded Medicaid, an additional 48,000 state residents would have been insured today, which would bring the uninsured rate down to 5.9%.

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7. Massachusetts
> Ppt change in uninsured rate, 2012-2015: -2.9 (approx.)
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 3.9% (the lowest)
> Pct. population without health insurance, 2015: <3.0% (2nd lowest)

An estimated 3.9% of Massachusetts residents did not have health insurance in 2012, the smallest uninsured rate at that time. As of March 2015, since the implementation of the Affordable Care Act, the percentage had fallen by an estimated 2.9 percentage points, the seventh smallest drop nationwide. At less than 3% as of March, the percentage of Massachusetts residents without health insurance remained the lowest in the country.

Massachusetts implemented its own health care reforms six years before the implementation of Obamacare. The state’s health insurance marketplace, Massachusetts Health Connector, has been helping to make insurance more affordable for state residents since its 2007 launch. Due to the state’s progressive policies regarding health insurance, relatively few state residents did not have health insurance in 2012, and the effect of the ACA was not as dramatic as it was in other states.

8. Delaware
> Ppt change in uninsured rate, 2012-2015: -3.2
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 8.8% (6th lowest)
> Pct. population without health insurance, 2015: 5.6% (11th lowest)

Nearly 80,000 Delaware residents did not have health insurance in 2012, or 8.8% of the state’s population — far lower than the national uninsured rate that year of 14.8%. As of March 2015, since the Affordable Care Act was implemented, that percentage had dropped 3.2 percentage points. While the improvement was more modest than the national decline of 5.7 percentage points, the uninsured rate remains among the lowest percentages in the nation. Earlier this year, Governor Jack Markell received approval from the HHS to take full control of Delaware’s health insurance marketplace.

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9. Minnesota
> Ppt change in uninsured rate, 2012-2015: -3.2
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 8.0% (4th lowest)
> Pct. population without health insurance, 2015: 4.8% (6th lowest)

Already before the ACA was enacted, Minnesota had a small uninsured population. An estimated 8.0% of Minnesota’s residents did not have health insurance in 2012, the fourth lowest rate. By March this year, the rate had fallen by 3.2 percentage points, the ninth smallest drop nationwide. The uninsured rate of 4.8% has remained among the lowest nationwide. In contrast, the percentage of Americans without health insurance fell by 5.7 percentage points over that period. Because of the ACA, 166,197 state residents have obtained health insurance, including new Medicaid recipients under the Medicaid expansion.

Minnesota implemented in 2013 its own health care exchange program, MNsure. The Minnesota Insurance Marketplace Act, which established the exchange program, stipulates that 1.5% of all premiums will fund MNsure’s operational expenses. This percentage increased to 3.5% at the beginning of this year.

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10. Oklahoma
> Ppt change in uninsured rate, 2012-2015: -3.3
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 18.4% (5th highest)
> Pct. population without health insurance, 2015: 15.1% (3rd highest)

Oklahoma’s rate of uninsured residents dropped from 18.4% in 2012 — fifth highest at the time — to 15.1% this year. The improvement, however, was not as strong as in other states, and Oklahoma’s rate of its uninsured population was third highest as of March this year.

Oklahoma did not set up its own health care exchange and it did not expand Medicaid benefits. According to the federal government, if Oklahoma expands Medicaid coverage, an additional 123,000 residents would gain coverage, and the uninsured rate would fall to 11.9%.

11. Wyoming
> Ppt change in uninsured rate, 2012-2015: -3.3
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 15.4% (17th highest)
> Pct. population without health insurance, 2015: 12.1% (10th highest)

In 2012, before the state’s Health Insurance Marketplace open enrollment period began, 15.4% of Wyoming’s population did not have health insurance. Today, 12.1% of people are uninsured, 3 percentage points higher than the nationwide rate of uninsured population 9.1%.

Wyoming is one of 20 states without an expanded Medicaid program under Obamacare. The state also did not develop its own exchange. Instead, residents must visit healthcare.gov to purchase health insurnace. According to Kowalski’s research, states that ceded full control of the ACA adoption to the federal government tended to have higher health care costs. A typical non-smoking, middle-aged male paid health insurance premiums of slightly less than $400 per month, the second-most expensive of any state.

12. Kansas
> Ppt change in uninsured rate, 2012-2015: -3.3
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 12.6% (21st lowest)
> Pct. population without health insurance, 2015: 9.3% (19th highest)

After the first open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased. In Kansas, the percentage of the population without health insurance decreased from 12.6% in 2012 to 9.3% as of March this year. The improvement of 3.3 percentage points was smaller than the national decline in the rate of uninsured Americans of 5.7 percentage points.

Unlike some states, Kansas was not proactive on health care reform. The state did not implement a state exchange nor did it expand Medicaid coverage. If Kansas expands Medicaid, an estimated 100,000 additional residents would gain health insurance and the uninsured rate would drop to 5.8%.

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13. Pennsylvania
> Ppt change in uninsured rate, 2012-2015: -3.5
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 9.8% (9th lowest)
> Pct. population without health insurance, 2015: 6.3% (17th lowest)

In 2012, before the state’s Health Insurance Marketplace open enrollment period began, 1.2 million Pennsylvania residents, or 9.8% of the population, did not have health insurance. Since then, the share of residents without health insurance coverage fell 3.5 percentage points to 6.3%. The percentage of Americans without health insurance dropped 5.7 percentage points over that period to 9.1%.

Former Pennsylvania Governor Tom Corbett expanded the state’s Medicaid program in August last year, and was one of a minority of Republican governors to do so. However, Corbett’s health plan was unusual compared to the Medicaid expansion in other states. Current Governor Tom Wolf, a democrat, overhauled the system early this year, and claims it now offers coverage to more state residents.

14. Missouri
> Ppt change in uninsured rate, 2012-2015: -3.5
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 13.6% (25th lowest)
> Pct. population without health insurance, 2015: 10.1% (15th highest)

Missouri did not expand Medicaid under Obamacare, and the state ceded full control of the act’s implementation to the federal government — residents must visit healthcare.gov to purchase health insurance. If the state elects to expand Medicaid, the federal government estimates an additional 253,000 Missouri residents would be covered and the uninsured share of the population would fall further to 5.8%.

Still, there was some improvement. Three years ago, 13.6% of Missouri residents did not have health insurance, the 25th lowest uninsured rate in the country. The rate improved during the open enrollment period, and today, 10.1% of Missouri’s population is without insurance, the 15th highest share of uninsured citizens of all states.

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15. Wisconsin
> Ppt change in uninsured rate, 2012-2015: -3.6
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 9.0% (7th lowest)
> Pct. population without health insurance, 2015: 5.4% (10th lowest)

Three years ago, 9.0% of Wisconsin residents did not have health insurance, the seventh lowest uninsured rate in the country. The rate further improved during the open enrollment period, and today, only 5.4% of Wisconsin’s population is without insurance, the 10th lowest share of all states. While average premiums were not significantly higher in states that did not expand Medicaid, the average premium for a 40-year-old, nonsmoking man was $308, fifth highest in the country.

16. Indiana
> Ppt change in uninsured rate, 2012-2015: -3.6
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 14.3% (22nd highest)
> Pct. population without health insurance, 2015: 10.7% (13th highest)

Nearly 1 million Indiana residents did not have health insurance in 2012, or 14.3% of the state’s population. As of March 2015, since Obamacare was implemented, that percentage had dropped by 3.6 percentage points, a smaller drop than the comparable national decline of 5.7 percentage points over that period.

Though Indiana did not establish its own state exchange, the federal government-run healthcare.gov helped more than 200,000 state residents purchase health insurance. The state did expand Medicaid, however, providing coverage for those making at or less than 138% of the federal poverty level.

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17. Louisiana
> Ppt change in uninsured rate, 2012-2015: -3.9
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 16.9% (12th highest)
> Pct. population without health insurance, 2015: 13.0% (5th highest)

In 2012, before the state’s Health Insurance Marketplace open enrollment period began, 759,627 Louisiana residents, or 16.9% of the population, did not have health insurance. Since then, the share of the uninsured population has fallen 3.9 percentage points to 13%, the fifth highest uninsured rate in the country. So far, the state government has not opted to expand Medicaid. If it does, 265,000 more people would be covered, and the uninsured rate would fall to 7.2%. The cost of health insurance is relatively high in Louisiana. The average monthly premium for a 40-year-old, nonsmoking man in the state in 2015 was $274, the 10th highest of any state.

18. New York
> Ppt change in uninsured rate, 2012-2015: -3.9
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 10.9% (14th lowest)
> Pct. population without health insurance, 2015: 7.0% (22nd lowest)

More than 2.1 million New York residents did not have health insurance in 2012, or 10.9% of the state’s population. As of March 2015, since the Affordable Care Act was implemented, that percentage had dropped by 3.9 percentage points — the 18th smallest drop in the country.

New York was one of a minority of states to set up its own health insurance exchange marketplace. During the designated open enrollment period, uninsured New Yorkers can go to the New York State of Health’s website to purchase coverage. All state-run exchanges were expected to be financially self-sustaining by this year. As part of the state’s 2015-2016 budget plan, Governor Andrew Cuomo announced a new tax on health insurance premiums to help fund the exchange.

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19. Alabama
> Ppt change in uninsured rate, 2012-2015: -3.9
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 13.3% (24th lowest)
> Pct. population without health insurance, 2015: 9.4% (18th highest)

In 2012, before the Health Insurance Marketplace open enrollment period began, 632,499 Alabama residents, or 13.3% of the population, did not have health insurance. Since then, the uninsured rate fell by 3.9 percentage points to 9.4%, slightly higher than the 9.1% of Americans who are currently uninsured.

Unlike most states, Alabama did not expand Medicaid under the ACA. Such an expansion would have likely helped a number of low-income residents obtain health insurance — 18.7% of Alabamians lived in poverty, the seventh highest rate nationwide. According to the U.S. government, expanding Medicaid would provide an additional 235,000 Alabama residents health coverage and lower the uninsured rate to 4.5%.

20. Virginia
> Ppt change in uninsured rate, 2012-2015: -4.1
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 12.5% (20th lowest)
> Pct. population without health insurance, 2015: 8.4% (24th highest)

In 2012, before the federal health insurance exchange open enrollment period began, 12.5% of the population did not have health insurance. Over the next three years, the rate of the uninsured population dropped 4.1 percentage points to 8.4%. In contrast, the percentage of Americans without health insurance dropped 5.7 percentage points over that period.

The state’s uninsured rate would drop further if Virginia opts to expand Medicaid coverage to those with incomes less than 138% of the poverty level. According to the HHS, an additional 210,000 Virginians would be covered if the state takes advantage of the federal funds for the expansion, lowering the uninsured rate to 5.8%.

21. Maine
> Ppt change in uninsured rate, 2012-2015: -4.2
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 10.2% (11th lowest)
> Pct. population without health insurance, 2015: 6.0% (13th lowest)

Maine was the only state in New England that did not take advantage of the federal incentives to expand Medicaid. This is especially significant for Maine, which had the lowest median household income in the region at $46,974. Expanding coverage from the current threshold of the federal poverty level to 138% of the federal poverty level would cover an additional 28,000 Maine residents, according to HHS estimates.

In 2012, before the state’s Health Insurance Marketplace open enrollment period began, 134,709 Maine residents, or 10.2% of the population, did not have health insurance. Since then, the uninsured rate dropped by 4.2 percentage points. In contrast, the percentage of Americans without health insurance dropped by 5.7 percentage points over that three-year period. While average premiums were not significantly higher in states that did not expand Medicaid, the average monthly premium for a 40-year-old, nonsmoking man in Maine was $272, 11th highest of any state.

22. North Dakota
> Ppt change in uninsured rate, 2012-2015: -4.2
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 10.0% (10th lowest)
> Pct. population without health insurance, 2015: 5.8% (12th lowest)

After open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased. The percentage of North Dakota’s population without health insurance decreased from 10.0% in 2012 to 5.8% as of March this year. In contrast, 9.1% of Americans do not have health insurance.

In addition to the adoption of the ACA and the expansion of Medicaid, North Dakota’s mining industry may also partly account for the decrease in the uninsured rate. People working in the mining industry are among the most likely to have health insurance compared to those in other industries. The number of mining jobs in North Dakota increased dramatically from 2012 through 2014. Mining employment started to contract at the start of the year, however.

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23. Utah
> Ppt change in uninsured rate, 2012-2015: -4.2
> Expanded Medicaid?: under discussion
> Pct. population without health insurance, 2012: 14.5% (20th highest)
> Pct. population without health insurance, 2015: 10.3% (14th highest)

Three years ago, 14.5% of Utah residents did not have health insurance, the 20th highest uninsured rate in the country. The rate improved during the open enrollment period, and today, 10.3% of Utah’s population is without insurance, the 14th highest share of uninsured citizens of all states. Out-of-pocket costs for those opting in are relatively low. The average premium for a 40-year-old, nonsmoking man was $207, the ninth lowest in the country.

Whether or not the state expands Medicaid is currently under discussion. If state officials move forward with the expansion, the HHS estimates an additional 74,000 state residents would gain health insurance coverage.

24. Mississippi
> Ppt change in uninsured rate, 2012-2015: -4.6
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 17.0% (11th highest)
> Pct. population without health insurance, 2015: 12.4% (7th highest)

An estimated 17.0% of Mississippi residents did not have health insurance in 2012, well above the national share of 14.8% that year. By March 2015, the percentage had fallen by 4.6 percentage points to 12.4%, the seventh highest rate of an uninsured state population in the country.

Despite Mississippi Commissioner of Insurance Mike Chaney’s expressed intention to establish a state insurance marketplace, the governor and the state’s legislature rejected the plan. In addition, Mississippi did not expand Medicaid coverage, a decision that would have had a relatively large impact in the state as Mississippi had the lowest median household income in the country at $37,963. If the state opted to expand Medicaid, an estimated 165,000 residents would gain coverage, and the uninsured rate would fall to 6.8%.

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25. Illinois
> Ppt change in uninsured rate, 2012-2015: -4.9
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 12.8% (23rd lowest)
> Pct. population without health insurance, 2015: 7.9% (25th lowest)

After open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased. In Illinois, the percentage of the population without health insurance decreased from 12.8% in 2012 to 7.9% as of March this year. Nationally, the uninsured rate fell 5.7 percentage points over the same period.

Opting for federal assistance in launching its state exchange, Illinois has received more than $150 million in federal grants to implement health care reforms. While nearly 600,000 Illinois residents are insured today as a result of the ACA, there is plenty of room for improvement. An estimated 1 million Illinois residents remain uninsured, one of the largest uninsured populations nationwide.

26. Texas
> Ppt change in uninsured rate, 2012-2015: -4.9
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 22.5% (the highest)
> Pct. population without health insurance, 2015: 17.6% (2nd highest)

In 2012, before the state’s Health Insurance Marketplace open enrollment period began, 5,762,358 Texas residents, or 22.5% of the population, did not have health insurance. At the time, this was the largest share of uninsured residents of any state.

Since then, the percentage of Texans without health insurance has decreased by 4.9 percentage points. Still, a relatively high 17.6% of Texas’ population remains uninsured, but the state no longer has the lowest health insurance coverage rate, beating only Alaska. Texas has not expanded Medicaid. If the state decides to do so, an estimated 1.2 million low-income Texas residents would gain health insurance, the largest projected increase in the nation.

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27. Michigan
> Ppt change in uninsured rate, 2012-2015: -5.0
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 11.4% (17th lowest)
> Pct. population without health insurance, 2015: 6.4% (18th lowest)

More than 1.1 million Michigan residents did not have health insurance in 2012, or 11.4% of the state’s population. As of March 2015, since the Affordable Care Act was implemented, that percentage had dropped by 5 percentage points, a slightly smaller drop than the national decline of 5.7 percentage points. Nevertheless, the state’s underinsured rate, at 6.4%, was nearly 3 percentage points below the rate of uninsured Americans. The low uninsured rate may be due to Michigan’s decision to expand Medicaid to more than 300,000 residents.

28. Tennessee
> Ppt change in uninsured rate, 2012-2015: -5.1
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 13.9% (23rd highest)
> Pct. population without health insurance, 2015: 8.8% (22nd highest)

Tennessee deferred to the federally managed health care exchange website and did not take advantage of the federal incentives to expand Medicaid coverage. According to the federal government, an additional 234,000 state residents would gain coverage if Medicaid is expanded in Tennessee, lowering the uninsured rate to 5.2%. Still, many more people are covered today in Tennessee because of the ACA.

In 2012, before the implementation of Obamacare, 13.9% of the population did not have health insurance. Since then, the uninsured rate has fallen by 5.1 percentage points to 8.8%, just lower than the nationwide uninsured rate of 9.1%. The average monthly premium for a 40-year-old, nonsmoking man in the state in 2015 was just $200, fifth lowest of any state.

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29. South Carolina
> Ppt change in uninsured rate, 2012-2015: -5.2
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 16.8% (13th highest)
> Pct. population without health insurance, 2015: 11.6% (11th highest)

South Carolina’s rate of uninsured residents dropped from 16.8% in 2012 — 13th highest at the time — to 11.6% this year, the 11th highest. The state has not opted to expand Medicaid coverage to the state’s nearly 200,000 individuals with incomes less than 138% of the federal poverty level. If these South Carolina residents were to become eligible for Medicaid, the uninsured rate would fall to an estimated 7.4%. South Carolina residents pay higher-than-average insurance premiums, with the typical 40-year-old male spending $268 per month.

30. Ohio
> Ppt change in uninsured rate, 2012-2015: -5.4
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 11.5% (19th lowest)
> Pct. population without health insurance, 2015: 6.1% (14th lowest)

An estimated 11.5% of Ohio residents did not have health insurance in 2012. By March this year, the percentage had fallen by 5.4 percentage points, inline with the nationwide drop. Ohio was among 31 other states to expand Medicaid under the ACA. As a result of the expansion, 587,000 individuals received health insurance.

Like most other states, Ohio residents must visit healthcare.gov to receive health insurance. Despite the lack of a state-specific health insurance exchange, Ohio’s Department of Insurance website provides useful links and information for state residents curious about Obamacare.

31. New Hampshire
> Ppt change in uninsured rate, 2012-2015: -5.4
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 10.6% (13th lowest)
> Pct. population without health insurance, 2015: 5.2% (9th lowest)

Though New Hampshire did not implement its own exchange marketplace, it expanded Medicaid coverage to those earning less than 138% of the federal poverty rate. As a result of the expansion, an estimated 43,000 low-income state residents gained health insurance.

Three years ago, 10.6% of New Hampshire residents did not have health insurance, the 13th lowest rate of uninsured population in the country. The rate improved during the open enrollment period, and today only 5.2% of New Hampshire’s population is without insurance, the ninth lowest share of all states. Out-of-pocket costs for health insurance recipients were inline with national costs. The average premium for a 40-year-old, nonsmoking man was $254 versus the national average of $256.

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32. Maryland
> Ppt change in uninsured rate, 2012-2015: -5.4
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 10.3% (12th lowest)
> Pct. population without health insurance, 2015: 4.9% (8th lowest)

After open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased. The percentage of Maryland’s population without health insurance decreased from 10.3% in 2012 to 4.9% as of March this year, the eighth smallest uninsured rate nationwide. In contrast, 9.1% of Americans do not have health insurance.

Preferring to manage its own exchange market, Maryland established the Maryland Health Connection in 2011. The state was rewarded for its early compliance, receiving $6.2 million Early Innovator grant from the federal government. However, according to Kowalski, Maryland’s exchange was one of five state websites to experience severe glitches. According to Kowalski’s research, website problems at the outset hurt enrollment numbers and increased costs.

33. New Jersey
> Ppt change in uninsured rate, 2012-2015: -5.5
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 12.7% (22nd lowest)
> Pct. population without health insurance, 2015: 7.2% (23rd lowest)

After open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased dramatically. In New Jersey, the improvement was relatively modest. The percentage of the population without health insurance decreased from 12.7% in 2012 to 7.2% as of March this year, the 18th smallest decrease nationwide.

In an effort to establish its own state-run exchange, the state legislature passed the New Jersey Health Benefit Exchange Act on October 18, 2012. However, Governor Chris Christie vetoed the bill, and New Jersey residents have to get coverage through the federal program.

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34. Montana
> Ppt change in uninsured rate, 2012-2015: -5.6
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 18.0% (8th highest)
> Pct. population without health insurance, 2015: 12.4% (8th highest)

Since open enrollment under the ACA began, Montana’s rate of uninsured residents dropped from 18.0% in 2012 — eighth highest at the time — to an estimated 12.4% this year. The improvement was not sharp enough to move Montana out of the 10 states with the highest share of uninsured residents, as the state still has the eighth highest share of uninsured residents.

The state did not opt to expand Medicaid under the Affordable Care Act, but if it had, the HHS estimates an additional 38,000 Montanans would have been covered today. While this would have strengthened the improvement in Montana, it is a relatively small projected increase and would not significantly change the uninsured rate.

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35. Georgia
> Ppt change in uninsured rate, 2012-2015: -5.9
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 18.4% (5th highest)
> Pct. population without health insurance, 2015: 12.5% (6th highest)

In 2012, before the state’s Health Insurance Marketplace open enrollment period began, 1,792,319 Georgia residents, or 18.4% of the population, did not have health insurance. Since then, the state’s uninsured rate dropped by 5.9 percentage point. The percentage of Americans without health insurance dropped by 5.7 percentage points over that three-year period. The state did not opt to expand Medicaid under the ACA. The HHS estimates that if Medicaid were to be expanded, it could provide an additional half a million low-income residents health insurance and the uninsured rate would drop to 7.7%.

36. Vermont
> Ppt change in uninsured rate, 2012-2015: -6.0 (approx.)
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 6.5% (2nd lowest)
> Pct. population without health insurance, 2015: <3% (the lowest)

Vermont’s rate of uninsured residents dropped from 6.5% in 2012 — second lowest at the time — to less than 3% this year, one of the lowest rates in the nation. Put another way, the number of uninsured residents went from 40,053 to roughly 3,000, a nation-leading 92.6% drop.

Many Vermonters would like even more comprehensive coverage. About four years ago, the state enacted a bill to put the nation’s first single-payer health care system into place. However, Governor Peter Shumlin recently rejected the proposed funding plan due to high projected costs.

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37. Arizona
> Ppt change in uninsured rate, 2012-2015: -6.0
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 17.6% (10th highest)
> Pct. population without health insurance, 2015: 11.6% (12th highest)

Arizona’s rate of uninsured residents dropped from 17.6% in 2012 — 10th highest at the time — to 11.6% this year. The improvement was slightly larger than the 5.7 percentage point decrease across the country.

Low-income individuals benefited the most from the ACA, and the improvement in Arizona would likely have been smaller if the state had not expanded Medicaid under the ACA. The state was one of 30 states to expand Medicaid. According to the U.S. government, 280,546 state residents have gained Medicaid coverage since open enrollment in the Health Insurance Marketplace began.

38. North Carolina
> Ppt change in uninsured rate, 2012-2015: -6.5
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 16.6% (14th highest)
> Pct. population without health insurance, 2015: 10.1% (16th highest)

North Carolina has not expanded Medicaid under Obamacare. With one of the lowest median household incomes in the country of $45,906, expanding coverage would likely have a relatively large impact on the state. According to the HHS, 377,000 low-income North Carolina residents would gain health insurance if the state expands Medicaid benefits.

Three years ago, 16.6% of North Carolina residents did not have health insurance, the 14th highest rate of uninsured residents in the country. The rate improved during the open enrollment period, and now only 10.1% of North Carolina’s population is without insurance, the 16th highest share of all states. Despite having strong participation in the system, out-of-pocket costs for those opting in are still relatively high. The average premium for a 40-year-old, nonsmoking man was $270, 12th highest in the country.

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39. Idaho
> Ppt change in uninsured rate, 2012-2015: -6.6
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 16.2% (16th highest)
> Pct. population without health insurance, 2015: 9.6% (17th highest)

Like just a dozen other states, Idaho opted to create its own health insurance marketplace to optimize coverage for its population. While several state-run health insurance exchanges experienced severe glitches, the improvement in the coverage rate was generally more successful in states that ran their own health insurance exchanges compared to states that rely on the federal government-run healthcare.gov. In 2012, before the Health Insurance Marketplace open enrollment period began, 254,743 Idaho residents, or 16.2% of the population, did not have health insurance. Since then, the state’s rate of uninsured residents dropped 6.6 percentage points. In contrast, the percentage of Americans without health insurance dropped 5.7 percentage points over that three year period.

40. Washington
> Ppt change in uninsured rate, 2012-2015: -7.7
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 13.9% (23rd highest)
> Pct. population without health insurance, 2015: 6.2% (15th lowest)

An estimated 13.9% of Washington residents did not have health insurance in 2012, about a percentage point lower than the national share at that time. By March this year, the share had fallen by 7.7 percentage points, the 11th largest drop nationwide. The state’s expansion of Medicaid was by far the largest contributor to the decline in the rate of the uninsured population. As of January, more than 500,000 low-income Washington residents gained health insurance under the expansion. Washington manages its own exchange program, Washington Healthplanfinder.

41. Rhode Island
> Ppt change in uninsured rate, 2012-2015: -7.7
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 11.1% (15th lowest)
> Pct. population without health insurance, 2015: 3.4% (3rd lowest)

In 2012, 114,865 Rhode Island residents did not have health insurance, or 11.1% of the state’s population. As of March 2015, since the Affordable Care Act was implemented, that percentage had dropped by 7.7 percentage points, a larger drop than the national decline of 5.7 percentage points over that period.

Governor Lincoln Chafee established Rhode Island’s insurance exchange program through an executive order. Rhode Island was one of eight states that took total control of the ACA implementation and Medicaid expansion. The state received nearly $140 million in federal grants, $35.6 million of which came from an Early Innovator grant.

42. Florida
> Ppt change in uninsured rate, 2012-2015: -7.9
> Expanded Medicaid?: no
> Pct. population without health insurance, 2012: 20.1% (4th highest)
> Pct. population without health insurance, 2015: 12.2% (9th highest)

In 2012, before the Health Insurance Marketplace open enrollment period began, 3.8 million Florida residents, or 20.1% of the population, did not have health insurance. Since then, the state’s uninsured rate dropped by 7.9 percentage points, well above the nationwide drop of 5.7 percentage points over that period.

Like most states in the Southeast, Florida did not expand Medicaid. Though Florida had one of the 10 largest percentage point decreases in its uninsured population, the HHS estimates that another 848,000 low-income Floridians would have been covered had the state’s government decided to take advantage of the federal funds and expand Medicaid.

While average premiums were not significantly higher in states that did not expand Medicaid, the average premium for a 40-year-old, nonsmoking man was $303, the sixth highest in the country.

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43. West Virginia
> Ppt change in uninsured rate, 2012-2015: -8.2
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 14.4% (21st highest)
> Pct. population without health insurance, 2015: 6.2% (16th lowest)

After open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased. The percentage of the population without health insurance decreased from 14.4% in 2012 to 6.2% as of March this year, the eighth largest decrease nationwide. Uninsured rates decreased the most among low-income Americans, and this was especially the case in West Virginia, where 18.5% of people lived in poverty, the 10th highest rate. More than 170,000 state residents received health insurance under the Medicaid expansion, making up the vast majority of the increase. The state did not develop its own health care exchange. Uninsured West Virginia residents need to go to the federal government’s site healthcare.gov to sign up for insurance.

44. Nevada
> Ppt change in uninsured rate, 2012-2015: -8.2
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 22.2% (2nd highest)
> Pct. population without health insurance, 2015: 14.0% (4th highest)

More than 600,000 Nevada residents did not have health insurance in 2012, or 22.2% of the state’s population. At the time, this was the second highest rate nationwide after Texas. As of March 2015, since the Affordable Care Act was implemented, that percentage had dropped by 8.2 percentage points, a more significant drop than the 5.7 percentage point decrease nationwide. Despite the drop, however, 14% of Nevada’s residents still do not have health insurance. Low-income residents were by far the largest group to benefit from the ACA. As a result of the Medicaid expansion, more than 200,000 people in the state now have health insurance.

Nevada’s state insurance marketplace, Nevada Health Link, experienced serious technical glitches upon its rollout. Despite the initial problems, the ACA has been beneficial, not only in terms of getting more Nevadans insured, but also in significant savings for seniors receiving Medicare benefits. According to the federal government, Nevada seniors have saved $87.7 million since the ACA’s implementation.

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45. Colorado
> Ppt change in uninsured rate, 2012-2015: -8.3
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 14.7% (19th highest)
> Pct. population without health insurance, 2015: 6.4% (19th lowest)

An estimated 14.7% of Colorado residents did not have health insurance in 2012. By March this year, the percentage had fallen by 8.3 percentage points to 6.4%, the sixth largest increase nationwide. The state’s recent expansion of Medicaid was by far the largest contributor to the decline in the rate of the uninsured state population. As of January, more than 400,000 low-income Colorado residents gained health insurance under the expansion.

Colorado was one of eight states to both implement its own state run exchange and expand Medicaid. The state received approximately $180 million in federal grants to implement its exchange program.

46. Arkansas
> Ppt change in uninsured rate, 2012-2015: -8.6
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 16.4% (15th highest)
> Pct. population without health insurance, 2015: 7.8% (24th lowest)

An estimated 16.4% of Arkansas residents did not have health insurance in 2012, the 15th highest rate at the time. By March this year, the percentage had fallen by 8.6 percentage points, the fifth largest drop nationwide. After the coverage increase, 7.8% of state residents still did not have health insurance, the 24th lowest share in the country. Low-income Arkansas residents were by far the largest group to benefit from the ACA. As a result of the Medicaid expansion, 268,000 state residents gained health insurance, the vast majority of the total improvement.

Arkansas was the first state to announce its intentions to partner with the federal government to roll out the Affordable Care Act. Recently, Governor Asa Hutchinson received approval from the HHS to take full control of the health insurance exchange. The program will be fully state-run by 2016.

47. California
> Ppt change in uninsured rate, 2012-2015: -9.0
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 17.9% (9th highest)
> Pct. population without health insurance, 2015: 8.9% (21st highest)

California established its own state-run exchange, Covered California, early on and expanded Medicaid. To assist the state with building its health insurance exchange and expansion programs, California received more than $1 billion in federal grants between 2010 and 2014.

In 2012, before the Health Insurance Marketplace open enrollment period began, 17.9% of California’s population did not have health insurance. Since then, the uninsured rate has fallen by 9 percentage points to 8.9%, just lower than the national rate. The state’s expansion of Medicaid was by far the largest contributor to the decline in the uninsured rate. As of January, more than 3 million low-income residents in California gained health insurance under the expansion.

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48. Oregon
> Ppt change in uninsured rate, 2012-2015: -10.1
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 14.9% (18th highest)
> Pct. population without health insurance, 2015: 4.8% (7th lowest)

An estimated 14.9% of Oregon residents did not have health insurance in 2012. By March this year, since the implementation of the Affordable Care Act, the percentage had fallen by 10.1 percentage points to 4.8%, the third largest drop nationwide. Low-income residents were by far the largest group to benefit from the ACA. As of January, since the state expanded Medicaid, more than 400,000 Oregon residents had received health insurance.

Oregon was one of five states that experienced significant technical issues with the roll out of its online exchange. Had the state exchange been implemented without a hitch, the 10.1 percentage point drop in the uninsured population may have been even larger.

49. New Mexico
> Ppt change in uninsured rate, 2012-2015: -10.2
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 18.4% (5th highest)
> Pct. population without health insurance, 2015: 8.2% (25th highest)

After open enrollment in the Health Insurance Marketplace began on October 1, 2013, health insurance coverage in every state increased. In New Mexico, the percentage of the population without health insurance decreased from 18.4% in 2012 to 8.2% as of March this year, the second largest improvement nationwide. With a poverty rate of 21.9% — the second highest nationwide — Medicaid expansion under the ACA had an especially large impact in New Mexico. As a result of the expansion, 230,000 New Mexicans received health insurance.

Initially, New Mexico opted to manage its own health care insurance exchange for small businesses, while the federal government managed the marketplace for individuals. Later, the state implemented its own all-encompassing exchange website, BeWellNM.com, for individuals and businesses.

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50. Kentucky
> Ppt change in uninsured rate, 2012-2015: -10.4
> Expanded Medicaid?: yes
> Pct. population without health insurance, 2012: 13.9% (23rd highest)
> Pct. population without health insurance, 2015: 3.5% (4th lowest)

Nearly 600,000 Kentucky residents did not have health insurance in 2012, or 13.9% of the state’s population. As of March 2015, since the Affordable Care Act was implemented, the percentage of Kentuckians without health insurance had dropped by 10.4 percentage points — the largest decline compared to other states. Kentucky was one of 31 states to expand Medicaid under the ACA, and low-income residents were among the primary beneficiaries of the legislation. Nearly half a million people gained health insurance as a result of the expansion.

The state also chose to run its own health care exchange, Kynect, which has been praised as among the best-run exchanges in the nation. Future reductions in the rate of the uninsured population largely depend on decisions from state officials, and future leaders could have a significant impact on the program’s success going forward, particularly in Kentucky. GOP gubernatorial candidate Matt Bevin recently vowed to dismantle the exchange and cancel the Medicaid expansion.

METHODOLOGY

To determine the states where the Affordable Care Act (ACA) has improved health insurance coverage the most, 24/7 Wall St. ranked states on the largest percentage point decline in uninsured rates from 2012 through 2015. Each year, the U.S. Census Bureau’s American Community Survey (ACS) calculates the proportion of the noninstitutional population that does not have health insurance. The noninstitutional population excludes those in prisons, retirement homes, mental facilities, or on active duty with the Armed Forces.

We used data from the Department of Health and Human Services (HHS) on the number of people in each state who are covered by an insurance plan as of March 2015 through a state or federal exchange. Also from the HHS, we included the number of people who have gained Medicaid coverage since the rollout of the ACA in October 2013. Even in states that did not approve of the Medicaid expansion as part of the ACA implementation, Medicaid coverage changed as people’s incomes fell below the federal poverty level.

To calculate the number of people who gained insurance since the rollout, we added the number of people who enrolled in a marketplace plan for 2015 and the number of people who gained Medicaid coverage since the beginning of the ACA implementation. To avoid significant overestimates due to double counting, we adjusted our 2015 insured population by about 26% to arrive at a net increase in health insurance coverage of roughly 17 million people nationwide. This figure is consistent with other estimates.

The uninsured population in 2015 was calculated by subtracting the insured population in 2015 from the uninsured population in 2012. Next, we projected growth in each state’s noninstitutional population for 2014 and 2015 in two rounds and used it to find the share of each state’s population that does not have insurance this year.

In many cases, Medicaid expansion had a significant impact on the decline of a state’s uninsured population. Whether or not a state expanded Medicaid came from the Kaiser Family Foundation, which reviewed each state’s health system in July 2015. For the state’s that did not expand Medicaid, the HHS provided estimates of the number of people who would become eligible for coverage if the state opts for expansion. In addition to our estimates of health insurance coverage, we also calculated what the uninsured rate would be if the state opted to expand Medicaid.

Additionally, we considered annual unemployment rates from 2011 through April 2015 from the Bureau of Labor Statistics. From the ACS, we reviewed the share of households earning less than $10,000 each year and the share of households earning more than $200,000. We also reviewed median household income, poverty rates, educational attainment rates, and the percentage of the population that received food stamps. All ACS data are for 2013, the most recent period for which data are available.

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