"The Actuarial Approach anticipates that a retiree's assets and liabilities will be re-measured at least once a year to adjust the retiree's budget for differences between actual and assumed experience, for differences between actual and assumed spending and for changes in assumptions. This re-measurement process is essential for keeping the retiree on track.... Depending on the proportion of a retiree's spending budget that is derived from accumulated savings invested in risky assets, differences between actual and assumed investment returns can have a significant effect on the retiree's spending budget."