Long before premiums began rising, companies that offer defined benefit pensions plans had been moving to freeze them (fixing participants' retirement benefits no matter how much longer they work) or closing them to new workers.
A survey released earlier this year by benefits consultant Aon Hewitt of nearly 250 employers representing 6 million employees found that, of the roughly three-quarters who still offer a defined benefit plan, a third were closing them and another third had frozen them.
Of the companies with plans that remained open, 14 percent of companies said they were "very likely" to close them this year, 9 percent said they were "very likely" to freeze them and 5 percent said there were very likely to terminate them. (Companies terminating plans typically offer participant a lump sum payout to replace the monthly defined benefit income.)
The trend continues a decade-long decline in defined benefit plans in favor of defined contribution plans like 401(k) retirement plans. That historic shift has been cited by some retirement researchers as a major reason for the deficit in retirement savings estimated by the Employee Benefits Research Institute at more than $4 trillion for U.S. households in which the breadwinner is between ages 25 and 64.
Read More For millions, 401(k) plans have fallen short
Companies that still offer their workers defined pension benefits are facing their own funding shortfall, with too little money set aside in pension assets to cover the cost of paying current and future retiree benefits.
Both public and private pension funds were hit hard by the 2008 financial crisis, which wiped out trillions of dollars in investments that were used to pay retiree benefits. Since then, low interest rates have cut returns and increased the amount of money needed to generate enough income to write monthly checks to retirees.
Underfunded pensions, of course, represent the biggest potential liability for the Pension Benefit Guaranty Corp., which steps in when a pension fund can no longer cover what it owes its participants. Many of the biggest shortfalls have hit older companies with declining profits and large pools of older workers and retirees. Of the 10 biggest pension takeovers by the agency in the last four decades, five were plans offered by airlines and four were pension plans for steel companies.