“Wisconsin taxable income” of natural persons means Wisconsin adjusted gross income less the Wisconsin standard deduction, less the personal exemption described under s. 71.05 (23), with losses, depreciation, recapture of benefits, offsets, depletion, deductions, penalties, expenses and other negative income items determined according to the manner that income is or would be allocated, except that the negative income items on individual or separate returns for net rents and other net returns which are marital property attributable to the investment, rental, licensing or other use of nonmarital property shall be allocated to the owner of the property.