SECTION 1. Section twenty-one hundred and seventy of the Administrative Code of nineteen hundred and seventeen is hereby amended to read as follows:
"SEC. 2170. Classification of municipalities—Number of councilors.—Municipalities are divided into five classes, according to their receipts, as follows: Municipalities of the first class shall be those the annual receipts of which averaged fifty thousand pesos or more during the last three years, and shall have eight councilors; of the second class, those the annual receipts of which averaged thirty thousand pesos or more, but less than fifty thousand pesos, during the last three years, and shall have eight councilors; of the third class, those the annual receipts of which averaged fifteen thousand pesos or more, but less than thirty thousand pesos, during the last three years, and shall have six councilors; of the fourth class, those the annual receipts of which averaged five thousand pesos or more, but less than fifteen thousand pesos, during the last three years, and shall have six councilors; of the fifth class, those the annual receipts of which averaged less than five thousand pesos during the last three years, and shall have four councilors : Provided, That the councilors elected at the last general election in each municipality shall continue to hold office during the term for which they were elected, and the reduction or increase of the number of councilors in accordance with the classification of municipalities prescribed in this Act shall take effect beginning with the general election of nineteen hundred and twenty-eight."