40 ILCS 5/12-135.3

On January 1 of each year, every surviving spouse, other than a surviving spouse who is receiving a temporary annuity or who has received a surviving spouse annuity for less than one full year, shall be entitled to a 3% annual increase in his or her surviving spouse's annuity. The 3% annual increase shall be based on the amount of annuity then payable, including any increases previously received under this Section.