The following property values shall be included in the ratio study:

(1) Assessed values. Values determined by county assessors according to the provisions of chapters 84.40 RCW (Listing of property) and 84.41 RCW (Revaluation of property).

(2) Forest land values. Values of forest land classified or designated under chapter 84.33 RCW and values of timberland classified under chapter 84.34 RCW.

(3) Current use values. Values of land (except timber land) and improvements classified under chapter 84.34 RCW (current use assessment). Values of land (except timber land) and improvements classified under chapter 84.34 RCW shall be included as a separate class for counties when those values equal or exceed fifteen percent of the total assessed value of locally assessed real property in the county.

(4) Advisory values. Advisory values supplied to the assessor by the department, but only if the property falls within the sales study provided for in WAC 458-53-070 or 458-53-100 or is selected in the appraisal or audit study in accordance with WAC 458-53-130 and 458-53-140.