N.D. Cent. Code § 15-39.1-10.10

An individual who on June 30, 1999, is receiving monthly benefits from the fund on an account paid under this chapter or under former chapter 15-39 is entitled to receive a monthly increase equal to an amount determined by taking two dollars per month multiplied by the member's number of years of service credit plus one dollar per month multiplied by the number of years since the member's retirement.