The division of the territory for electoral purposes must respect a basic democratic principle: the effective representation of electors. The Act respecting elections and referendums in municipalities provides for a number of rules making it possible to ensure effective representation. The equality of the votes of electors and respect for natural communities are the two criteria set out in this act.
The equality of the votes of electors is an important prerequisite for effective representation. Each electoral district must have roughly an equal number of electors.
However, this equality is relative as variations in relation to the average number of electors per electoral district are allowed. Under the Act, the number of electors in an electoral district must deviate by not more than 25% from the average for municipalities with less than 20,000 inhabitants and by not more than 15% for municipalities with over 20,000 inhabitants.
The equality of the votes of electors alone cannot guarantee effective representation. Electoral districts must represent natural established communities based on geographic, demographic and socioeconomic criteria.
The electoral districts must thus be delimited in a way that ensures the greatest socioeconomic homogeneity possible of each, taking into account criteria such as physical barriers, demographic trends, borough limits, parish limits, the area and distance.