The most popular health plans on the Affordable Care Act (ACA)’s exchanges, silver-level plans, will require 34 percent higher premiums on average in 2018, according to an analysis from Avalere Health. The average hike for the second-lowest-priced silver plans, often considered the benchmark for the exchanges, will be 38 percent.

Many ACA enrollees will be shielded from the hikes by the law’s premium support subsidies. Unsubsidized enrollees could find less drastic hikes with bronze or gold plans, which will see premium hikes of 18 percent and 16 percent, respectively.

“Plans are raising premiums in 2018 to account for market uncertainty and the federal government’s failure to pay for cost-sharing reductions,” Caroline Pearson, senior vice president at Avalere, said in a statement. “These premium increases may allow insurers to remain in the market and enrollees in all regions to have access to coverage.”

The biggest jump in silver plan premiums is in Iowa, where monthly prices will rise by an average of 69 percent. In three states, the average premium decreased: Alaska (22 percent drop), Arizona (6 percent drop) and North Dakota (4 percent drop).

Among all metal tiers, the average monthly premium has increased substantially since 2015. Bronze plan rates went from $373 per month in 2015 to $561. Silver plans rose from $453 to $743. Gold plans went from $530 to $831. Platinum plans—the least popular ACA plans which cover 90 percent of customers’ health costs but are chosen by fewer than 1 percent of enrollees—have seen premiums increase from $645 in 2015 to $1,125 in 2018.

The Congressional Budget Office had predicted another double-digit hike in premiums ahead of the Nov. 1 start date for open enrollment on account of uncertainty among insurers that cost-sharing reduction subsidies would continue to be paid—a fear which was realized when President Donald Trump halted the payments in October. Sens. Lamar Alexander, R-Tennessee and Patty Murray, D-Washington, have proposed a plan to alleviate some of the 2018 hikes by funding the CSRs for two years, with rebates from insurers included to gain back portions of the premium hikes which were based on CSRs being pulled.