Obamacare customers could pay 18 percent more on average for their plans next year and have fewer insurers to choose from, a new analysis finds.

Proposed 2018 exchange premiums for the silver plan, the most popular of Obamacare’s three metal plan tiers, are 18 percent higher than this year, according to an analysis from the healthcare research firm Avalere. The data is based on the eight states that have submitted early rate filings from insurers.