Wilshire said that the monthly change in funding resulted from a 0.8 percent increase in liability values versus relatively flat asset values (-0.1 percent). The year-to-date decrease in funding is the result of an 8.6 percent increase in liability values.

Increasing discount rates and relatively flat equity markets were responsible for the increase, according to Mercer, which said that as of May 31, the estimated aggregate deficit of $498 billion decreased by $6 billion as compared to the end of April.

The aggregate deficit is still up by $94 billion, it added, from the $404 billion deficit measured at the end of 2015.

And the LIMRA Secure Retirement Institute reported that U.S. group pension buyout sales totaled $1.084 billion in the first quarter of the year—the first time, it said, that sales have topped $1 billion in the first quarter since 2008, and the fourth consecutive quarter in which sales have exceeded $1 billion.

Although in a blog post Michael Ericson, analyst for LIMRA Secure Retirement Institute, said that in addition to large plans, increasing numbers of small and medium-size plans are transferring their pension risk, it remains to be seen whether that heady pace will continue if the numbers continue to fall—since funded status is the first metric assessed in buyout deals.

But it certainly is on the mind of numerous experts. Despite reporting an increase in funded status, Mercer is certainly keeping lackluster performance in mind. "As we have said for a while now," Jim Ritchie, partner, retirement, Mercer, said in a statement, "plan sponsors should consider adapting their pension management policies to include the possibility that long-term rates may stay low for quite some time into the future and that the risk premium for equities may not make a significant improvement in funded status anytime soon."

Ritchie added, "Plan sponsors should continue to consider risk transfer and LDI [liability-driven investment] strategies as effective risk management tools in the short-term."