WASHINGTON — Average premiums for individual insurance plans on the national exchange created by the Affordable Care Act will be down next year after major spikes in 2017 and 2018.

According to a new report by the Centers for Medicare & Medicaid Services (CMS), the price for a benchmark "silver" plan through the federal HealthCare.gov site will be an average of 1.5 percent lower in 2019 after rising 37 percent in 2018.

There's wide variation from state to state. In Tennessee, premiums are down 26 percent after a 56 percent increase the previous year. In North Dakota, they're up 20 percent after an 8 percent increase in 2018. Open enrollment for plans begins Nov. 1 and runs through Dec. 15.

“President Trump’s administration took action to address the skyrocketing price of health insurance, and now we are starting to see the results,” CMS administrator Seema Verma said in a press release.

But much of the drop-off is due to companies raising premiums too much in 2018, experts say, amid a chaotic period when Republicans came close to repealing Obamacare and President Donald Trump announced plans to "let Obamacare implode" in order to pressure Democrats politically.

During this time, a number of insurers pulled out of markets entirely, briefly leaving some areas with no plans before state officials managed to attract replacements, in some cases by approving large premium hikes. This year, more insurers are expanding their presence instead. Thirty-nine percent of counties have only one insurer, versus 56 percent in 2018.

Democrats countered that the premiums would be even lower absent moves by the administration that experts say likely increased them.

“Here's the simple truth: People buying health insurance in America today are paying more for it than they should because of the relentless sabotage campaign by the Trump administration and its Republican allies in Congress and the states,” Leslie Dach, chair of the progressive group Protect Our Care, said in a statement.

Trump has recently claimed credit for stabilizing markets, but independent analysts say a number of White House actions increased premiums, including ending the individual mandate to buy insurance, cutting off payments to insurers for lower deductibles and promoting alternative short-term plans that do not have to cover pre-existing conditions.

"Premiums are going down because insurers overshot with premium increases this year that were too high," Larry Levitt, senior vice president for health reform at the Kaiser Family Foundation, said on Twitter. “Premiums would be even lower if not for repeal of the individual mandate penalty and expansion of short-term plans.”

Other administration moves most likely contributed to the premium decrease, however, including approving state plans to stabilize their markets.