The ridings are regularly reorganized according to the results of each decennial national census; however, the "senatorial clause" of the Constitution Act, 1867 guarantees each province at least as many MPs as it has senators, and the "grandfather clause" permits each province as many MPs as it had in either 1976 or 1985.
Izborne jedinice redovito se reorganiziraju nakon svakog popisa stanovništva koji se održava svakih 10 godina - iako, ustavni akt iz 1867. g. osigurana svakoj provinciji isti broj zastupnika koliko imaju i senatora, a tzv. "djedovska klauzula" (eng. "grandfather clause") dopušta da svaka provincija ima najmanje isti broj zastupnika kao što je imala 1976. ili 1985. godine.