The total pension funding shortfall at big U.S. companies has been varying widely this year and could be much higher at the end of the year than it was at the beginning.[@@]

Brad Klinck, a defined benefit pension expert at Aon Corp., Chicago, gives that assessment in a comment on the performance of defined benefit pensions at U.S. Fortune 100 companies.

The pension funding deficit could increase to $129 billion Dec. 31, up from $78 billion a year earlier, Klinck predicts.

The funding deficit has increased partly because interest rates are still low and returns on stocks and bonds have been weak, Klinck says.

But Klinck says regulatory uncertainty is partly to blame: Big corporations fear that any pension reform measures adopted this year somehow will penalize employers that make contributions this year.