The biggest driver of the trend in recent years is the growing number of companies that are deciding to end their plans, McDermott said.
As retirees live longer and the legal and financial cost of maintaining pensions rise, corporations are keen to jettison them.
The problem for companies looking to offload is that the pension plans must be fully-funded before they can sell them. GM, for example, had to inject more than $2.8 billion into its pension before closing a 2012 transfer to Prudential. It also paid Prudential a $2.1 billion fee for taking on the assets.
GM's current U.S. pension plan that is still held by the company is underfunded by $7.2 billion.
Surging stock markets and rising interest rates are making it easier for companies to replenish their pension plans but there are still gaps. The average corporate pension fund was 82 percent funded as of Jan. 31, according to Mercer Investment Consulting.
This article was provided by Reuters.