Setting realistic discount rates for calculating future liabilities is fundamental to creating healthier public pension systems, but the price tag will be high, according to recommendations from the Rockefeller Institute of Government.

Changing the way the discount rate is set to reflect the riskiness of expected benefits payments would likely cause a $2 trillion rise in reported liabilities for state and local retirement systems across the U.S., the institute, a part of the State University of New York, said.

By valuing liabilities at a rate that assumes no risk, the institute said taxpayers would have a better idea of the state of the pension funds. Such a discount rate would raise the annual total bill for governments to fully fund their systems by $100 billion. The institute cautions that that figure would be lessened or increased depending on how well riskier investments did in a given year.