The number of plans funded less than 65 percent increased during the period, to 264 plans from 214 plans. That group now represents more than 20 percent of the nation’s multiemployer plans, and has an aggregate funding deficit of $77 billion, more than half of the $151 billion deficit for all plans.

Of those critical, or “red zone” plans—the designation given by the Pension Benefits Guaranty Corp. to plans funded below 65 percent—Milliman reviewed recent data available for about half of that group.

Milliman found that 76 plans can expect to eventually go insolvent: 31 plans will be unable to meet pension obligations sometime before 2025; 32 are projected to be insolvent by 2034; and another 13 are expected to go under after that. The total funding shortfall of those plans is $28 billion.

The funding shortfall of plans expected to be insolvent is likely to grow, said Milliman. Excess returns, significant increases in participant and employer contributions, or benefit suspensions available to qualifying plans under the 2014 Multiemployer Pension Reform Act could impact when or if the worst funded plans go under.

Despite the preponderance of headlines detailing the plight of the worst funded collectively bargained plans, many remain in good shape, as 685 plans are funded above 80 percent, down from 794 in June 2015. And 192 plans are funded at more than 100 percent.

The funded status of all plans continues to be driven largely by investment performance, the report says.

For all funds, returns in 2016 need to be 5.5 percent to maintain the current aggregate funded status of 75 percent. Plans would need to enjoy double-digit returns this year to return to a 79 percent funded status.

A hypothetical and typical multiemployer pension portfolio was down 3 percent for the first two months of 2016, though the report notes markets have improved since March.