Investment increase; how determined

(1) A taxpayer shall be deemed to have made an increased investment in this state to the extent the value of the property used or available for use exceeds the value of all property used or available for use on the last day of the taxable year previous to the date the application was filed.

(2) To determine the value of property owned by the taxpayer, the tax basis before allowance for depreciation shall be used. To determine the value of property rented by the taxpayer, the average net annual rent shall be multiplied by the number of years of the lease for which the taxpayer was originally bound, not to exceed ten years. The rental of land included in and incidental to the leasing of a building shall not be excluded from the computation.

(3) Only investment in improvements to real property and tangible personal property that are depreciable under the Internal Revenue Code shall be considered.

(4) Vehicles, planes, or railroad rolling stock shall be excluded in determining the investment under this section.