(2) Notwithstanding any provision of law to the contrary, for fiscal years commencing April first, nineteen hundred eighty-eight, April first, nineteen hundred eighty-nine and April first, nineteen hundred ninety the actuarial value of assets shall be calculated using the five year smoothing method that was used for the fiscal year commencing April first, nineteen hundred eighty-seven which method has been determined to be actuarially sound.