The sharp fall in yields on the government long bond--the benchmark for deciding whether company pension funds are properly funded--could cost companies plenty by:

-- Forcing big cash payments into plans that become technically underfunded

-- Increasing the size of lump-sum payments to employees leaving the plans

-- Raising insurance premiums due to the Pension Benefit Guaranty Corp.

-- Triggering extensive corporate disclosure, including advance notice of mergers

Data: American Academy of Actuaries, Milliman USA