The director shall annually determine percentages to apply as a basis for determining the assessed valuation of class five property described in section 42-12005 equal to the ratios that the total net assessed valuation of all taxable property for primary and secondary tax purposes in class one and class six, paragraph 3 and personal property in class two bears to the total limited valuation used for primary tax purposes of such property, and that ratio shall be used for primary tax purposes as required by federal law.