Read: California pension fix leads to risk

By contrast, four states and the District of Columbia contributed less than 2 percent of total spending. North Dakota spent 1.63 percent and Vermont 1.76 percent of total spending, the two lowest levels of contributions among state pension plans.

On average, NASRA’s report says pensions “do not comprise a significant portion of state and local spending.”

But that assessment may be misleading, according to Andrew Biggs, an economist with the American Enterprise Institute, a Washington, D.C.-based conservative think tank.

“The reality is that if state and local governments were truly fully funding their pensions – that is, merely following the rules that the federal government requires for corporate pensions – their annual contributions would make up over 20 percent of total state and local government spending,” writes Biggs in a Forbes column.

Contribution requirements for private and public pensions are based on, in part, substantially different discount rates, which are used to determine the cost of future obligations. The Government Accounting Standards Board issues public plan guidelines.

Corporate plans use and average rate of 3.8 percent, while state and local public plans use and average rate of 7.7 percent, according to Biggs.

Private plans are also required to amortize pension debt over seven years, while public pensions debt obligations are based on a 30-year schedule, Biggs says. The shorter schedule private plans must follow increases near-term contribution costs, and assures a quicker path to fully funded status.

By Biggs’ numbers, were state and local plans beholden to the stricter private sector pension plan requirements, their annual contributions would be four times as much.

The discrepancy between public and private pension funding requirements is based on the logic that governments can’t fail, whereas corporations can.

Biggs thinks that logic is questionable, siting bankruptcies in Detroit and Puerto Rico as evidence.

“When a government low-balls its contributions by assuming high rates of return on risky investments and then amortizes investment losses over 30 years, it’s doing nothing other than making future taxpayers fund the pension benefits that current taxpayers should have paid for,” writes Biggs.

“The reason (state and local) pension contributions are seemingly low is quite simply (because) these governments aren’t fully funding their pensions,” he adds.

NASRA says that more than $250 billion is paid out annually to public sector pension participants.

The National Association of State Retirement Administrators says taxpayer contributions to the country’s state and locally sponsored public pension funds totaled 4.1 percent of general spending in 2013, according to recently updated research.