Whenever a census taken under an act of Congress shall show that the population of a city, town or village has increased or diminished so as to take or place such city, town or village out of the class to which it theretofore has belonged, the governing authorities of the municipality shall enter an order on the minutes thereof reciting such fact and adjudging the proper class of such municipality according to such census, and shall forward a certified copy of such order to the secretary of state, who shall file same with the other records pertaining to such municipality and keep same as a permanent record. Thereafter, such municipality shall be classed according to the population shown by such census, and such census shall be conclusive on the question of such classification.