(1) Each county assessor must cause taxable real property characteristics to be reviewed in accordance with international association of assessing officers standards for physical inspection and valued at least once every six years in accordance with RCW
84.41.030, and in accordance with a plan filed with and approved by the department of revenue. Such revaluation plan must provide that all taxable real property within a county must be revalued and these newly determined values placed on the assessment rolls each year. Property must be valued at one hundred percent of its true and fair value and assessed on the same basis, in accordance with RCW
84.40.030, unless specifically provided otherwise by law. During the intervals between each physical inspection of real property, the valuation of such property must be adjusted to its current true and fair value, such adjustments to be made once each year and to be based upon appropriate statistical data.
(2) The assessor may require property owners to submit pertinent data respecting taxable property in their control including data respecting any sale or purchase of said property within the past five years, the cost and characteristics of any improvement on the property and other facts necessary for appraisal of the property.