(a) For members, as of June 30 in each year, commencing June 30, 1987, a determination shall be made of the increase, to the nearest one-tenth of a percent of the Consumer Price Index for the preceding fiscal year. The retirement allowance of each beneficiary in receipt of an allowance for at least one year on the next following December 31 shall be increased by an amount equal to one-half of the percentage increase. The increase shall commence on the January 1 immediately following such December 31. The adjustment shall apply to members of the Group A, B, or D plans receiving an early retirement allowance only in the year following attainment of normal retirement age, provided the member has received benefits for at least 12 months as of December 31 of the year preceding any January adjustment. The maximum adjustment of any retirement allowance resulting from any such determination shall be two percent for Group A members and three percent for Group B, C, and D members, and no retirement allowance shall be reduced below the amount payable to the beneficiary without regard to the provisions of this section.

(b) For purposes of this section, Consumer Price Index shall mean the Northeast Region Consumer Price Index for all urban consumers, designated as "CPI-U," in the northeast region, as published by the U.S. Department of Labor, Bureau of Labor Statistics.

(c) No adjustment shall be made pursuant to this section in a deferred vested allowance payable pursuant to subsection 5059(a) of this title prior to its commencement.

(d) For all members of Group A and Group B, who have retired prior to July 1, 1987, there is hereby granted on July 1, 1989 a cost of living adjustment to each member's retirement allowance equal to two percent for each year of retirement prior to July 1, 1987 but not to exceed a total adjustment greater than ten percent.

(e) No adjustment shall be made pursuant to this section in January if the Consumer Price Index as of the previous June 30th is a negative rate. (Added 1987, No. 39, § 9; amended 1989, No. 11, § 9; 1991, No. 233 (Adj. Sess.), § 7; 1999, No. 61, § 5; 2005, No. 197 (Adj. Sess.), § 8; 2009, No. 139 (Adj. Sess.), § 10a; 2011, No. 63, § H.3.)