Each disability benefit payable under Section 15-150 and calculated under Section 15-153 or 15-153.2 that has not yet received an initial increase under this Section shall be increased by 0.25% of the monthly disability benefit multiplied by the number of full months that have elapsed since the benefit began on January 1, 2002 or the January 1 next following the granting of the benefit, whichever occurs later.
     On each January 1 following the initial increase under this Section, the disability benefit shall be increased by 3% of the current amount of the benefit, including prior increases under this Article.
     The changes made to this Section by this amendatory Act of the 92nd General Assembly apply without regard to whether the benefit recipient was in service on or after the effective date of this amendatory Act.