The monthly benefit to be paid under early retirement shall be based on the actual age in years and months the retirement member has attained on the date retirement benefits are to begin. The reduction factor is based on a level interpolation, between ages 55 and 62 for members whose first participating service occurs before November 1, 2011, and between ages 60 and 65 for members whose first participating service occurs on or after November 1, 2011.
Okla. Admin. Code § 590:10-7-4