SEATTLE (AP) - The board for Washington's health-insurance exchange has approved an average rate increase of 24 percent, the largest premium increase since the exchange began in 2013.

The Washington Health Benefit Exchange board approved the rate increase this week.

The Seattle Times reports about 180,000 customers will be affected.

Health exchange spokesman Michael Marchand says the increase is primarily due to rising costs for prescription drugs.

Last year, rate increases averaged 11 percent. In 2016, the rate rose by 4 percent and in 2015, it rose by 1 percent.

Customers can also expect fewer insurance providers to choose from going into 2018. King, Pierce and Snohomish counties each lost three providers and Kitsap County lost one.

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