On July 1, 1971, the retirement salary of each person retired prior to July 1, 1965, under the provisions of section 31-283 or any predecessor statute shall be increased in the amount of that percentage of the monthly retirement salary being paid to him on June 30, 1967, which was provided under section 5-162b for members of the state employees retirement system who retired in the same year as such person. On July 1, 1972, and annually thereafter, the retirement salary of each such person shall be adjusted to reflect increases or decreases in the Consumer Price Index in the same manner and to the same extent that the retirement salary of persons retired under chapter 66 is adjusted under section 5-162c.