 This takes place at least once every 7 years, or when the state's entitlement to the number of members of the House of Representatives changes.Boundaries are drawn by a Redistribution Committee, and apportionment within a state is on the basis of the number of "enrolled voters" rather than total residents or "population".The number of enrolled voters in each division cannot vary by more than 10% from the average across a state or territory, nor can the number of voters vary by more than 3.5% from the average projected enrolment 3.5 years into the future.