Average rates for popular health plans sold under the Affordable Care Act will fall 1.5% next year, according to the Trump administration, the first such drop and a sign that the insurance markets are gaining firmer traction despite tumult in the past two years.

The decrease will affect average premiums for the second-cheapest plans in the “silver” tier, a middle-cost option, after years of double-digit increases. In contrast, the average rate for those plans increased by 37% between 2017 and 2018, the administration said.

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