Milliman found that, although 2014’s strong market helped increase funded status by more than 4 percent, 2015 has been flat from an equity standpoint.

In addition, the study found that the trend among many public plan sponsors of reducing return assumptions for the future may “[reflect] today's market realities but also creates a steeper hill to climb if these pensions are to reach full funding.”

“These pensions had a decent year in 2014, but given the early returns in 2015, the road ahead could be challenging for the 66 percent of these plans that are less than 80 percent funded,” Becky Sielman, author of the study, said in a statement.

Sielman added, “Many public plans have become more realistic about return assumptions in recent years—the median return assumption has decreased from 8.00 percent in 2012 to 7.65 percent this year—which will further steepen the climb to full funding, especially for the 10 percent of our study that are currently less than 50 percent funded.”

The study also highlighted what the firm termed a “significant milestone” for these largest U.S. public pension plans. It’s the first time that retired and inactive members covered by the plans actually outnumber those active employees still earning benefits.

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That doesn’t paint a pretty picture, since the accrued liability for those retirees, according to the study, outpaces the accrued liability for employees by more than 40 percent in aggregate.