Oregon Revised Statutes Revenue and Taxation § 308.233

(1) For purposes of making a physical appraisal of property for ad valorem property taxation, in arriving at the value level for the property, any sales data used shall be examined, analyzed, adjusted and otherwise utilized in such a manner that the value level determined for the property is substantially equivalent to the value level that would be determined if the sales data utilized was the same sales data, and was examined, analyzed, adjusted and otherwise utilized in the same manner as the sales data utilized in making the certified ratio study under ORS 309.200.

(2) The purpose of this section is to achieve equality and uniformity in assessed values between properties that are physically appraised and those that are not physically appraised, but subject to trending or indexing for the particular assessment year.