S.D. Codified Laws § 3-12C-1502
On an annual basis, at minimum, the board shall establish an interest rate assumption upon which the provisions of subsequent supplemental pension contracts shall be based. The board shall establish the assumption on the basis of the recommendations of the system's actuary and the state investment officer. The interest rate assumption may not be greater than the actuarial assumed rate of return for the fund, nor may the interest rate assumption be less than the effective rate of interest. Any other provision of law notwithstanding, the board may suspend issuance of new supplemental pension contracts at any time. Any suspension of new supplemental pension contracts shall be prospective in operation and may not affect supplemental pension contracts already in effect.
The administration of the supplemental pension benefit requires that supplemental pension benefit purchase costs vary from one time period to the next. Consequently, participants who accept the option of a supplemental pension benefit have no expectation or fundamental right to any particular supplemental pension benefit purchase price.
SDCL 3-12C-1502