S.D. Codified Laws § 58-17-34
There may be a provision as follows: "Relation of earnings to insurance: If the total monthly amount of loss of time benefits promised for the same loss under all valid loss of time coverage upon the insured, whether payable on a weekly or monthly basis, shall exceed the monthly earnings of the insured at the time disability commenced or his average monthly earnings for the period of two years immediately preceding a disability for which claim is made, whichever is the greater, the insurer will be liable only for such proportionate amount of such benefits under this policy as the amount of such monthly earnings or such average monthly earnings of the insured bears to the total amount of monthly benefits for the same loss under all such coverage upon the insured at the time such disability commences and for the return of such part of the premiums paid during such two years as shall exceed the prorata amount of the premiums for the benefits actually paid hereunder; but this shall not operate to reduce the total monthly amount of benefits payable under all such coverage upon the insured below the sum of two hundred dollars or the sum of the monthly benefits specified in such coverages, whichever is the lesser, nor shall it operate to reduce benefits other than those payable for loss of time."
SDCL 58-17-34