As in the valuation of all other classes of tangible property for ad valorem tax purposes, market value is the assessment goal. To attain that goal, the trade level concept for inventory and leased equipment shall be considered.

Trade level may be defined as value at the point in the production stream where an item of manufactured personalty is found, or the production-distribution level in which a product is found.

In appraising tangible personal property, the assessor shall give recognition to the trade level at which the property is situated and to the principle that tangible property normally increases in value as it progresses through production and distribution channels. Such property normally attains its maximum value as it reaches the consumer level.

Raw material in the hands of the processor or manufacturer should be valued at their cost to the owner or to a competitor.

Work in process in the hands of the processor or manufacturer shall be valued at the stage of production where found (costs to date) or cost to a competitor.

Finished goods held for sale shall be valued at the amount for which they would transfer to a like business (cost to produce); those held for lease or rental shall be valued at the trade level of the principal user, usually cost to retailer or consumer.

Where personal property is in the hands of a person engaged in two or more of the functions of producer, manufacturer, processor, wholesaler, or retailer, the assessor shall determine the level of trade at which the property is situated on the assessment date by reference to its form, location, quantity, and probable purchasers or lessees.

Livestock all county assessors shall use the livestock schedule published annually for their district by the department of revenue as a guide in the valuation of livestock. The assessor must not use the average inventory basis of valuation in the assessment of livestock. (AGO 1-17-51)

Petroleum products all county assessors shall use the petroleum products schedule, approved annually by the department of revenue and adjusted to market zones within the state as a guide in the valuation of petroleum products.

Average inventory where the stock of goods, wares, merchandise or material, whether in a raw or finished state or in process of manufacture, owned by a taxpayer on January 1st of any year does not fairly represent the average stock carried by such taxpayer, such stock shall be listed and assessed upon the basis of the monthly average of stock owned or held by such taxpayer during the preceding calendar year or during such portion thereof as the taxpayer was engaged in business. (RCW 84.40.020) Although the taxpayer may request that the average inventory method be used and the assessor must comply with that request, whatever method is used—average inventory or inventory on January 1st—That method must be followed from year-to-year in reporting unless a showing is made that a major change in the business has occurred necessitating use of the other method.