If benefits paid to an individual are based on wages paid by two or more employers who are liable for payments in lieu of contributions, the amount of benefits payable by each such employer shall be an amount which bears the same ratio to the total benefits payable to the individual as the total base-period wages paid to the individual by such employer bear to the total base-period wages paid to the individual by all of his base-period employers.
SDCL 61-5A-20