A new analysis by Josh Rauh at Stanford University's Hoover Institution says state and local governments’ collective unfunded pension liabilities are actually about three times the amount they claim. Rauh, a finance professor who has long been a critic of public pension accounting, arrived at his figure by assigning pension plans a much lower assumed investment rate of return.

Pension plans in 2015 collectively reported about $1.3 trillion in unfunded liabilities. In other words, they have about 72 percent of the assets they need to meet their estimated total liabilities. That figure assumes plans will earn an average of 7.4 percent each year on their investments.

Rauh, pointing to the wild swings of the stock market and the fact that pensions are putting more of their assets into volatile, alternative investments, says that assumption is too risky. He argues it's more responsible to consider a rate of return closer to what long-term bonds earn: slightly less than 3 percent. Under those assumptions, Rauh says unfunded U.S. public pension liabilities would roughly triple to $3.8 trillion, or less than half-funded.