In Australia, a redistribution is the process of redrawing the boundaries of electoral divisions for the House of Representatives arising from changes in population and/or the number of representatives. There are no redistributions for the Senate as each state constitutes an at-large electorate with multiple members (senators). The Australian Electoral Commission (AEC), an independent statutory authority, oversees the apportionment and redistribution process for federal electorates, taking into account an array of demographic and geographic factors.AEC - Redistribution overview Politicians, parties and the general public may make submissions to the AEC on proposed boundaries, but any interference with their deliberations is considered a serious offence. The AEC’s decisions on boundary changes are final, and cannot be rejected or amended by the parliament. To do so would require an amendment to the electoral act itself; however, no government has ever altered the act with the intent of interfering in the redistribution process. In this way, partisan gerrymandering is widely regarded as a non-issue in Australian federal politics.
Section 24 of the Constitution of Australia specifies that the number of members of the House of Representatives in each state is to be calculated based upon their population, although each state is entitled to a minimum of five members regardless of population. This minimum condition currently only applies to Tasmania, the smallest state. Representation of territories has been specified by supplemental legislation. After the number of members for each state and territory is determined, in a process called apportionment or determination, they are divided into a corresponding number of electoral divisions.
A redistribution (sometimes called redrawing or "revision") of the geographic boundaries of divisions in a state or territory takes place when an apportionment determination results in a change in the number of seats to which a state or territory is entitled, at least once every seven years, or earlier when the AEC determines that population shifts within a state or territory have caused some seats to have too many or too few voters. The Commonwealth Electoral Act 1918 requires that all electoral divisions within a state or territory have approximately an equal numbers of enrolled voters. The Commonwealth Electoral Act (No. 2) 1973 reduced the allowed variation of electors in each division to 10% of the state or territory's average, down from 20%.Commonwealth Electoral Act (No. 2) 1973, s.4 New boundaries apply only to general elections held after the redistribution process has been finalised, and by-elections are held based on the previous electoral boundaries.
Each state and territory has its own electoral commission which follows similar but not identical processes and principles for determining boundaries and conducting elections within their jurisdiction, and those of local governments.
Redistribution triggers Section 59 of the Commonwealth Electoral Act 1918 outlines the timing on when redistribution should commence.
A redistribution of divisions in a State, the ACT or Northern Territory is required or triggered in three circumstances:Commonwealth Electoral Act 1918, s.59 if there has been a change in the number of parliamentary representatives to which the State or Territory is entitled, due to a change in population or an increase in the overall number of members, subject to the minimum number of divisions in original States. Under Sections 46 and 48 of the Act, these are determined by the Electoral Commissioner within 13 months after every first meeting of the House of Representatives ("determination"). if the number of electors in more than one third of the divisions in the State or one of the divisions in the Territory deviates from the respective State/Territory's average divisional enrolment by more than 10% for a period of more than two months ("malapportionment") if seven years has elapsed since the previous redistribution
However, despite the above requirements or triggers, a redistribution is not to commence in a State, the ACT or Northern Territory in two circumstances: if a redistribution of divisions is already undergoing in the State or Territory, otherwise the new redistribution would terminate the undergoing redistribution if it is within the twelve month period prior to the expiration of the House of Representatives.
For the latter circumstance, if the elapse of seven years since the previous redistribution falls within the twelve month period, the redistribution will instead be automatically deferred and commence within 30 days after the first meeting of the next House of Representatives. This is to prevent a general election from occurring while a redistribution is in progress.
Section 59 also states three additional circumstances: if a redistribution is triggered in a State or Territory anytime within 13 months after the first meeting of House of Representatives met (any of the triggers, including within 30 days after the first House of Representatives meeting as above) the determination of the seat entitlement has not been made yet (which has to be 12–13 months after the first sitting) the three-person Electoral Commission makes a judgement that there may be a change in seat entitlement for the State or Territory
If all of the three requirements are met, then the Electoral Commission can decide to defer the redistribution for the State and Territory until after the seat entitlement has been determined.
Example of redistribution deferrals From the above legislative requirements, this means that a redistribution can be deferred up to two times. An example of this was the redistribution in the ACT between 2012–2014. ACT had a redistribution on 9 December 2005, which meant that the following scheduled redistribution was to start around December 2012. The first House of Representatives sitting of the 43rd Parliament was on 27 September 2010, meaning the House of Representatives was due to expire on 27 September 2013. December 2012 fell within the twelve month period prior to the expiration (27 September 2012 to 27 September 2013), which meant that the scheduled redistribution was automatically deferred to within 30 days after the first House of Representatives sitting in the 44th Parliament.
The 44th Parliament eventually began on 12 November 2013. Within the following 30 days, the Electoral Commission made a judgement that there was possibility of a change in seat entitlement for ACT. The Commission then chose to defer the redistribution again until the determination could be made in another twelve months time (November–December 2014). The redistribution for ACT finally commenced in December 2014, two years after its scheduled commencement.
Malapportionment Under Section 58 of the Commonwealth Electoral Act 1918, after the end of every month, the Electoral Commissioner is to ascertain (on the same day):Commonwealth Electoral Act 1918, s.58 the number of electors enrolled in each division (in respect of each State/Territory) the average divisional enrolment of each State/Territory (i.e. total enrolment of the State/Territory divided by the number of the divisions in the State/Territory) the percentage deviation between the above two for each division
These numbers are required to be published in the Gazette monthly. Ascertainments are based on existing divisions and includes any finalised redistributed boundaries and created divisions at the time of ascertainment. An example of this is the gazette published in November 2024 for the number of electors as of 31 October 2024. The redistributions and boundaries for New South Wales, Victoria and Western Australia had just recently been finalised within the month prior. The October 2024 ascertainment included the new seat of Bullwinkel and excluded the abolished seats of Higgins and North Sydney, even though these would not come into effect until the 2025 election.
Under Section 59 of the Commonwealth Electoral Act, if the number of electors in more than one third of the divisions in a State or one of the divisions in a Territory deviates from the respective State/Territory's average divisional enrolment by more than 10% for a period of more than two months, this is considered malapportionment and is one of the three possible triggers for redistribution for that State or Territory.
Total number of members Section 24 of the Constitution specifies that the total number of members of the House of Representatives shall be "as nearly as practicable" twice as many as the number of senators. High Court rulings have later interpreted this section of the Constitution to apply to state members and senators. However, the principle of the House of Representatives roughly double of the Senate can still be applied when including territory members and senators.
As there are 72 state senators, there should be roughly 144 state members of the House of Representatives. When including the 4 territory senators, there should be roughly 152 members of the House of Representatives. The total number of members of the House of Representatives, and consequently electorates, varies from time to time. Every time there is a change in the number of members, a redistribution is required to be undertaken, except in Tasmania which has always had the constitutional minimum number of five members. At the first federal election, there were 75 members of the House of Representatives (for 65 divisions). In 1949, the number was increased from 74 to 121 (excluding the Australian Capital Territory and the Northern Territory), and in 1984 it was increased from 125 to 148.Representation Act 1983 Following the 2017 apportionment, the total number of members increased from 150 to 151, which was reversed following the 2023 apportionment.
Entitlement of states and territories The AEC determines the number of members to which each state and territory is entitled, which is based on the population of each state and territory. The day when it is exactly one year and one day after the first sitting day for a new House of Representatives is known as the "reference day". On this day (or the next earliest weekday if the reference day is a weekend or public holiday in the ACT), the Electoral Commissioner ascertains the most recent population estimate for each state and territory from the Australian Bureau of Statistics, in a process termed "ascertainment".Commonwealth Electoral Act 1918, Section 46: Ascertainment of numbers of people of Commonwealth, States and Territories Based on these figures, the AEC then makes its apportionment determination ("determination"), which is to be done "as soon as possible" after the ascertainment .The absolute latest a determination could be made is one month after the ascertainment.Commonwealth Electoral Act 1918, s.48
Section 24 of the Constitution requires that electorates be apportioned among the states in proportion to their respective populations; provided that each Original State has at least 5 members. Section 29 of the Constitution forbids electorate boundaries from crossing state lines. The current apportionment method is now found in section 48 of the Commonwealth Electoral Act 1918.Australian Electoral Commission.Research Report 4 – Australian Federal Redistributions 1901–2003. Accessed 5 May 2008.
Under the current method, the AEC firstly calculates a quota, as follows:
State entitlements After the quota is calculated, the number of members to be chosen in each State is the number of people of the State divided by the quota, and if on such division there is a remainder greater than one-half of the quota, one more member shall be chosen in the State.Calculating representation entitlements of states and territories