"Actuarial tables": Tables of mathematical functions derived from mortality, disability and turn-over rates, combined with interest discount factors as adopted by the board on recommendation of the actuary.
The adopted actuarial tables shall be used to determine the amount of all benefits under this Article, including any optional forms of benefits. Optional forms of benefits must be the actuarial equivalent of the normal benefit payable under this Article.
40 ILCS 5/14-103.19