The country’s 100 biggest public defined benefit pension plans experienced a funding increase of $185 billion in the first quarter, thanks mainly to robust investment gains of 7.3% in aggregate, Milliman, a consulting and actuarial firm, reported Monday.

This improvement was the largest quarterly funding increase since Milliman rolled out its public pension funding index in September 2016. It came on the heels of the biggest quarterly decrease of $306 billion in the fourth quarter.

Milliman estimated that first quarter investment returns of the public DB plans ranged from a low of 3.5% to a high of 11.6%. As a result, it reported, their funding status climbed from 67.2% at the end of December to 71% at the end of March.

In a statement, the index’s author Rebecca Sielman said that even with the market fluctuations of the past six months, it was important to remember that the pensions have time horizons measured in decades.

“Plan sponsors should take this volatility as a reminder to review their asset smoothing policies, to ensure the short-term market fluctuations don’t translate into short-term contribution volatility,” Sielman said.

At the end of March, the PPFI deficit stood at $1.508 trillion, compared with $1.693 trillion at the end of December. Milliman reported that total pension liability continued to grow, to an estimated $5.205 trillion at the end of the first quarter, up from $5.164 trillion at the end of previous quarter.

Fourteen PPFI plans had funded ratios above 90% in the first quarter, six more than in the previous three-month period.

At the lower end, 28 plans had funded ratios below 60%, with nine plans stuck below 40% funded.

Fifty-eight plans, one less than in the fourth quarter, were funded between 60% and 90%.