Principal councils have the power to make a community governance review at any time for all or part of their district. It is envisaged that such reviews will occur at intervals of between 10 and 15 years, and will take into account population changes, the need for well-defined boundaries and the wishes of local inhabitants. Reviews may also be triggered by a petition of local government electors for an area. A petition is deemed valid where it is signed by a sufficient proportion of the electorate (ranging from 50% in an area with fewer than 500 electors to 10% in one with more than 2,500). The sufficient proportion of the electorate necessary in areas with more than 2,500 electors was reduced from 10% to 7.5% under an amendment to the Act made in 2015.