Section 22C. A domestic life insurance company subject to the investment privilege excise imposed by section twenty-two B having admitted assets of two hundred million dollars or less at the close of a taxable year, shall be allowed a credit against such excise in the amount of twenty thousand dollars. Any such company, whose admitted assets at the close of a taxable year are in excess of two hundred million dollars, shall be allowed a credit against such excise in the amount of twenty thousand dollars, reduced pro rata by five hundred dollars for each one million dollars or fraction thereof by which the value of the admitted assets of such company at the close of the taxable year exceeds two hundred million dollars. For the purpose of this section admitted assets shall be valued by the commissioner of corporations and taxation in accordance with standards established with respect to annual statements under chapter one hundred and seventy-five.