The state's MNsure health insurance exchange said open enrollment got off to a smooth start Thursday, with more than 27,000 visits to the government-run website as of midafternoon.

Callers seeking help by phone waited an average of 1 second, MNsure said.

Across the country, the launch of open enrollment Thursday at MNsure and exchanges for all 50 states came at a time of uncertainty for the federal Affordable Care Act (ACA) due to legal and regulatory changes under the Trump administration. Even so, MNsure officials said there's a chance for enrollment growth since premiums in Minnesota will be lower.

"We're having a really successful open enrollment," said Nate Clark, the chief executive at MNsure, during an interview Thursday. "We haven't had any kind of issues or interruptions."

About 155,000 state residents purchase individual health insurance policies, which are an option for people under age 65 who are self-employed or don't get coverage from their employer.

The market saw significant changes starting in 2014 when the ACA made it illegal for health insurers to deny coverage to individuals with pre-existing health conditions.

Back in 2014, about 293,000 Minnesotans bought individual coverage. The market has shrunk by nearly half since then due to a series of big premium increases.

In Minnesota, open enrollment for shoppers buying individual health insurance policies for 2019 stretches through Jan. 13. The coverage is sold directly by some health insurers as well as through the MNsure exchange, which the state of Minnesota launched as part of the federal health law.

As of July, about 100,000 people in Minnesota's individual market were buying through MNsure, where about two-thirds of enrollees use federal tax credits that discount their premium costs. Individuals earning up to $48,560 per year, or a family of four earning up to $104,000 per year, could qualify for the subsidies.

In the past, opening day for MNsure sign-ups was much more stressful for consumers, with website problems in some cases and allegations two years ago of "robocallers" jamming the phone lines. While those years saw scores of complaints about MNsure on social media websites, there were no obvious signs of distress Thursday.

The website traffic numbers released Thursday afternoon were ahead of last year's counts, although the exchange this year also opened an hour earlier.

Affordability of coverage in the individual market has been a growing problem in Minnesota. After the state saw some of the lowest rates in the nation during 2014, carriers imposed big premium increases for three years and the market became considerably smaller as a result.

Rates for 2018 in the state, however, were either flat or down somewhat and premiums will be down more significantly next year.

The Kaiser Family Foundation said the average benchmark premium across Minnesota in 2019 for a 40-year-old nonsmoker will be $326 per month, a decline of 15 percent from the comparable rate this year. Across the country, the average monthly premium for a 40-year-old nonsmoker next year will be $477, a decline of less than 1 percent.

The improvement in Minnesota has come with a cost to taxpayers.

Over a two-year period, the state is spending $542 million on a reinsurance program that helps keep premiums low by covering some costs for people in the market with unusually expensive treatment needs.

There was a high degree of uncertainty surrounding the ACA in 2017 as congressional Republicans came close to repealing the law. The legislative effort failed, but Republicans passed a tax bill in late 2017 that President Donald Trump signed into law, which will eliminate the ACA's financial penalties for people who lack coverage next year.

This year, the Trump administration has developed rules that allow for expanded access to insurance coverage that doesn't comply with ACA rules. These policies might carry lower premiums for consumers, but they also run the risk of pulling healthy people from the ACA markets.

"Those plans are able to deny people with pre-existing conditions [and] charge more based on health status," said Cynthia Cox, a researcher with the California-based Kaiser Family Foundation. "They're more like plans that existed before the ACA."

Even so, some insurers are entering ACA markets, after several years when exits by insurers drove the story of the health law's insurance exchanges. And after several years of trying to get premiums to catch-up with the cost of medical claims, some carriers now how have set rates so high they couldn't justify further increases, Cox said.

At S&P Global Ratings, analysts expect individual market enrollment going forward will hold steady across the country at about 9 million people.

"We believe the market is now over the hump," S&P analyst Deep Banerjee said of individual coverage under the ACA. "The market is on a far more stable footing now."

Christopher Snowbeck • 612-673-4744 Twitter: @chrissnowbeck