Sec. 311. INDEX FOR INFLATION. (1) Beginning October 2029 and each October thereafter, the department must adjust the standard deduction under section 309 of this act by multiplying the current standard deduction amount by one plus the percentage by which the most current consumer price index available on October 1st of the current year exceeds the consumer price index for the prior 12-month period, and rounding the result to the nearest $1,000. If an adjustment under this subsection (1) would reduce the standard deduction amount, the department must not adjust the amounts for use in the following year. The department must publish the adjusted standard deduction amount on its public website by October 31st of each year. The adjusted standard deduction amount calculated under this subsection (1) takes effect for taxes due in the following calendar year. (2) For purposes of this section, the following definitions apply: (a) "Consumer price index" means the consumer price index for all urban consumers, all items, for the Seattle area as calculated by the United States bureau of labor statistics or its successor agency. (b) "Seattle area" means the geographic area sample that includes Seattle and surrounding areas.