(a) For all Group A members, as of June 30th in each year, beginning June 30, 1972, the Board shall determine any increase or decrease, to the nearest one-tenth of one percent, in the ratio of the average of the Consumer Price Index for the month ending on that date to the average of the Index for the month ending on June 30, 1971, or the month ending on June 30th of the most recent year subsequent thereto. In the event of an increase, and provided that the net increase following the application of any offset as provided in this subsection equals or exceeds one percent, the retirement allowance of each beneficiary in receipt of an allowance for at least one year on the next following December 31st shall be increased by an equal percentage. Such increase shall begin on the January 1st immediately following that December 31st. An equivalent percentage increase shall also be made in the retirement allowance payable to a beneficiary in receipt of an allowance under an optional election, provided the member on whose account the allowance is payable and such other person shall have received a total of at least 12 monthly payments by such December 31st. In the event of a decrease of the Consumer Price Index as of June 30th for the preceding year, the retirement allowance of a beneficiary shall not be subject to any adjustment on the next following January 1st; provided, however, that:

(b) For Group C members, as of June 30th in each year, commencing June 30, 1981, a determination shall be made of any increase or decrease, to the nearest one-tenth of a percent of the Consumer Price Index for the preceding fiscal year. In the event of an increase, and provided that there exists a net increase following the application of any offset as provided in this subsection, the retirement allowance of each beneficiary in receipt of an allowance for at least one year on the next following December 31st shall be increased by an amount equal to one-half of the net percentage increase. The increase shall commence on the January 1st immediately following that December 31st. The increase shall apply to Group C members having attained 57 years of age or completed at least 25 years of creditable service as of June 30, 2010, and receiving an early retirement allowance only in the year following attainment of age 62, and shall apply to Group C members not having attained 57 years of age or having completed at least 25 years of creditable service as of June 30, 2010, and receiving an early retirement allowance only in the year following the member's attainment of 65 years of age, provided the member has received benefits for at least 12 months as of December 31st of the year preceding any January adjustment. In the event of a decrease of the Consumer Price Index as of June 30th for the preceding year, the retirement allowance of a beneficiary shall not be subject to any adjustment on the next following January 1st; provided, however, that:

(c) For purposes of subsection (a) of this section, the maximum amount of any increase or decrease utilized to determine the net percentage increase shall be five percent. For purposes of subsection (b) of this section, the maximum amount of any increase or decrease utilized to determine the net percentage increase shall be five percent, and any increase or decrease less than one percent shall be assigned a value of one percent.

(d) As used in 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. (Added 1971, No. 233 (Adj. Sess.), § 1; amended 1981, No. 41, § 35; 1989, No. 169 (Adj. Sess.), § 8; 1991, No. 64, § 8, eff. June 18, 1991; 1991, No. 247 (Adj. Sess.), § 5; 1999, No. 158 (Adj. Sess.), § 13; 2009, No. 74 (Adj. Sess.), § 7; 2009, No. 139 (Adj. Sess.), §§ 6a, 6b, 7, 13; 2011, No. 63, § H.2; 2015, No. 114 (Adj. Sess.), § 7.)