Notwithstanding Section 20178, for member deaths occurring on or after January 1, 1994, if the actuarial interest rate exceeds 6 percent, the accumulated contributions of a member payable pursuant to subdivision (a) of Section 21532 shall be increased by a factor determined by the board that is based on the difference between the current actuarial interest rate defined in Section 20014 and the 6 percent interest crediting rate on member contributions. If the actuarial interest rate is less than 6 percent, no increase may be provided under this section.