(b) Whenever it shall appear by any decennial census that a county has attained a population entitling it to an advance in classification, or whenever it shall appear by the last two preceding censuses that a county has decreased in population so as to recede in classification, as provided in this section, it shall be the duty of the Governor, under the great seal of this Commonwealth, to certify that fact accordingly, to the commissioners on or before the first day of October of the year succeeding the year in which the census was taken, which certificate shall be forwarded by the commissioners to the recorder of deeds and be recorded in the recorder's office. It is the intent of this section that the classification of any county shall not be changed because its population has decreased at the time of one United States decennial census, because it is recognized that a change in the form of local government is attended by certain expense and hardship, and the change should not be occasioned by a temporary fluctuation in population, but rather only after it is demonstrated by two censuses that the population of a county has remained below the minimum figure of its class for at least a decade.