For the purposes of this chapter, the population of a city shall be the number of residents shown by the figures released for the most recent official state or federal census, by a population determination made under the direction of the office of financial management, or by a city census conducted in the following manner:

(1) The legislative authority of any such city may provide by ordinance for the appointment by the mayor thereof, of such number of persons as may be designated in the ordinance to make an enumeration of all persons residing within the corporate limits of the city. The enumerators so appointed, before entering upon their duties, shall take an oath for the faithful performance thereof and within five days after their appointment proceed, within their respective districts, to make an enumeration of all persons residing therein, with their names and places of residence.

(2) Immediately upon the completion of the enumeration, the enumerators shall make return thereof upon oath to the legislative authority of the city, who at its next meeting or as soon thereafter as practicable, shall canvass and certify the returns.

(3) If it appears therefrom that the whole number of persons residing within the corporate limits of the city is ten thousand or more, the mayor and clerk under the corporate seal of the city shall certify the number so ascertained to the secretary of state, who shall file it in his or her office. This certificate when so filed shall be conclusive evidence of the population of the city.

Population determinations, office of financial management: Chapter 43.62 RCW.