State and local governments coping with years of underfunding and weak investment returns will be forced to clarify the extent of pension deficits under rules set Monday that will widen the gaps for some plans.

The measures adopted by the Governmental Accounting Standards Board alter methods of calculating liabilities and assets by the retirement systems. The changes will mean pensions for public workers in Illinois, New Jersey, Indiana and Kentucky have less than 30 percent of assets needed to meet liabilities, according to the Boston College Center for Retirement Research.

The board voted unanimously to make the changes, starting next year, during a teleconference.