"Surplus to policyholders" for the purposes of this chapter, in addition to the insurer's capital and surplus, shall be deemed to include any voluntary reserves which are not required pursuant to law, and shall be determined from the last sworn statement of the insurer on file with the director, or by the last report of examination of the insurer, whichever is the more recent at time of assumption of risk.
SDCL 58-13-3