(1) Qualifying air and water pollution control property, gasohol facilities, qualifying research and development firms, and electrolytic reduction facilities real property included in class five will be revalued annually. The department will apply an annual appraisal trending factor to the qualifying property to arrive at the market value. An annual appraisal trend factor will be calculated, using the January cost indices from the Marshall & Swift Valuation Service Guide (Marshall & Swift Guide), for the current tax year. If the Marshall & Swift Guide is not available, other accepted cost manuals or indices may be used.

(2) The annual appraisal trend factor will be applied to the previous year's market value to arrive at the current year's market value.