The administrative cost of the South Carolina Retirement System, the South Carolina Police Officers Retirement System, the Retirement System for members of the General Assembly of the State of South Carolina and the Retirement System for Judges and Solicitors of the State of South Carolina shall be funded from the interest earnings of the above systems. The allocation of the administrative costs of the systems shall be made by the Budget and Control Board and shall be based upon a proration of such cost in proportion to the assets that each system bears to the total assets of all of the systems for the most recently completed fiscal year.