The top ObamaCare exchange insurers in six states where 2016 rate requests have already been filed are seeking to raise rates an average 18.6% next year.

Early reports range from an alarming 36% hike sought by the dominant insurer in Tennessee, to a hefty 23% average increase requested by Oregon insurers, to a moderate 7.7% average rise proposed in Connecticut.

The very limited data and the possibility that these initial requested rates might change, as they did in a significant way last year, make it hard to draw firm conclusions. But so far it appears that the Congressional Budget Office was on target in projecting a significantly bigger overall increase than in 2015.

The CBO has said it expects ObamaCare exchange premiums to rise an average of 8.5% per year over the next three years. That's partly due to the scheduled phasing-out of temporary government programs to protect insurer bottom lines from high-cost enrollees.

BlueCross Tennessee Wants 36% Hike

BlueCross BlueShield of Tennessee is seeking a 36.3% premium hike for its 165,000 members, comprising 70% of the market, the Tennessean reported. A check of HealthCare.gov shows that only Humana (HUM), which is asking for a 15.8% increase, offers a silver plan in Memphis within 40% of the cheapest BCBS offering.

For anyone who doesn't get subsidies, these increases would deliver a shock. The vast majority who do get subsidies will be shielded from higher premiums because their contribution is a fixed percentage of income, leaving the government to pay the difference.

On Friday, Maryland said that CareFirst is seeking premium hikes of close to 30% for the nearly 80% of exchange members it covers. The No. 2 insurer on the Maryland Health Connection, Kaiser Permanente, proposed a modest 4.8% increase.

In Michigan, where the individual market is dominated by Blue Cross Blue Shield of Michigan and its Blue Care HMO, insurers want an estimated 9.8% premium hike.

Data for Michigan, Connecticut and Oregon come from Charles Gaba’s ACASignups.net. He's calculating the weighted average increase, which puts more emphasis on rate changes requested by plans with the most members. ACASignups includes in its totals the ObamaCare-compliant plans offered off the exchanges. Those members also are generally part of the same risk pool, meaning their costs also influence exchange premiums.

Moda's Costs Exceeded Premiums By 61.5%

The talking point over the past year among ObamaCare supporters is that the 2015 rate increases were far smaller than those in the pre-ObamaCare era — an average of 5.4%, according to PricewaterhouseCoopers. But the Oregon State Public Interest Research Group told the Bend Bulletin that rate hikes proposed for 2016 were the highest since 2010.

While regulators in several states exerted their authority with some force to cut proposed 2015 rate hikes last year, they may not be able to do so to the same degree this time because insurers are setting rates based on actual market experience.

Moda Health, which serves just over 100,000 exchange enrollees, or close to 50% of Oregon's individual market, is seeking a 25.6% average premium increase. Its 2014 results help explain why: Moda's 2014 costs exceeded premiums by 61.5% in Oregon, even after receiving temporary government reinsurance payments to offset the cost of the sickest patients.

Moda wasn't the only Oregon insurer swamped by ObamaCare costs. LifeWise, the next biggest player with 17% of the market, is seeking to raise premiums 37.8%.

Still, even in Oregon, it's not clear that the hefty premium hikes will be a disaster for customers, because most people are eligible for subsidies. The Oregonian reported that new market entrant Zoom Health will now offer the lowest-priced silver plan to a 40-year-old in Portland, at $233 a month. Meanwhile, LifeWise wants to hike its premium from $222 a month to $318.

It will take another year or so to learn whether LifeWise and Moda were too pessimistic about the health of the enrollees who will sign up in 2016, or whether Zoom Health is too optimistic. Or perhaps Zoom, which has a growing chain of neighborhood clinics, thinks it can provide care more efficiently.

While rate requests also are in from Washington state insurers, the data are harder to assess because the state insurance department doesn't provide comparisons if an insurer significantly changes a plan's features.

Premera Blue Cross, the largest player in Washington with about 80,000 members, or one-fourth of the individual market, is seeking a 9.6% increase. All of the other players with a significant market share are listed as having new plans, except one. Group Health, with about 48,000 enrollees, plans to cut rates by about 4%.