Redistribution (Australia)

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.[9]

${\displaystyle {\mbox{Quotient of each state}}={\frac {\mbox{Population of each state }}{\mbox{Quota}}}}$

In simpler terms, the entitlement of each state is the quotient rounded to the nearest whole number. However, each Original State is entitled to a minimum of 5 members, a provision that gives Tasmania two additional seats than its population would otherwise justify.[10]

Until 2020, the quotient and entitlement of each territory was obtained using a similar rounding method to the one used for the states. In 2003, a statistical error margin — equal to twice the standard error of the population estimate — was added to the quotient for each territory. This margin was provided by the Australian Bureau of Statistics. The quotient and the error margin were added and rounded off to the nearest whole number to determine the entitlement for each territory. These provisions enabled the Northern Territory to retain its second seat at the 2004 federal election, and the Australian Capital Territory to gain a third seat at the 2019 federal election.[11]

The Electoral Amendment (Territory Representation) Act 2020, passed on 9 December 2020,[12][13] amended the Commonwealth Electoral Act 1918 to additionally apply the "harmonic mean method" in calculating each territory's entitlement. The method is also known as Dean’s Method.[14] The inclusion of the statistical error margin was also abolished.

The calculation of the territory's quotient is first determined in the same way used for state entitlement:

${\displaystyle {\mbox{Quotient of each territory}}={\frac {\mbox{Population of each territory }}{\mbox{Quota}}}}$

In accordance with Section 48 of the Commonwealth Electoral Act 1918, the calculation of the entitlement of each territory varies on the quotient calculated:

• If the quotient is less than or equal to 0.5, then the territory is not entitled to have a member of the House of Representatives. An exception applies to the Northern Territory and Australian Capital Territory, which are entitled to a minimum of 1 member each.[11]
• If the quotient is greater than 0.5, but less than or equal to 1, the territory is entitled to one member of the House of Representatives
• If the quotient is more than 3, then the entitlement of the territory is the quotient rounded to the nearest whole number (same method as state entitlement)
• If the quotient is more than 1, but less than or equal to 3, the entitlement is calculated via the harmonic mean method below. If the quotient is larger than its corresponding harmonic mean, then the entitlement is the quotient rounded up to the nearest whole number; otherwise, the entitlement is the quotient rounded down to the nearest whole number.[15][16]

${\displaystyle {\mbox{Minimum number of members}}={\mbox{Quotient rounded down to the nearest whole number}}}$

${\displaystyle {\mbox{Harmonic mean}}={\frac {\mbox{2 x Minimum number of members x (Minimum number of members + 1)}}{\mbox{Minimum number of members + (Minimum number of members + 1)}}}}$

Quotient	Minimum number of members	Harmonic mean	Seat Entitlement
1 to 1.3332	1	1.3333	1
1.3333 to 2			2
2 to 2.39	2	2.4000	2
2.40 to 3			3

Under the new rules adopted in December 2020, the Northern Territory with a quota of 1.4332 will retain two seats at the next Australian federal election.[12][17] It would have lost one seat under an AEC determination made in July 2020.[18]

The latest apportionment determination was made in July 2020. On 18 June 2020, the Bureau of Statistics had provided the AEC with population figures for December 2019. In the 2020 apportionment, Western Australia lost a seat to 15 seats and Victoria gained a seat to 39. Under the determination, the Northern Territory would have lost one of its two seats.[18] However, an amendment in December 2020 changed the method for determining the apportionment for the territories, which had the effect of reversing the loss of the seat for the Northern Territory.[12] The number of seats by States in the House of Representatives arising from the 2020 determination, with the change in law relating to the territories, were as follows:

State	Population June 2020 ('000)[19]	Seats	Change
New South Wales	8,164.1	47
Victoria	6,694.9	39	1
Queensland	5,174.4	30
Western Australia	2,661.9	15	1
South Australia	1,769.3	10
Tasmania	540.6	5
State Total	25,005.2	146
Australian Capital Territory	431.1	3
Northern Territory	246.0	2
Other	4.7	-
Total	25,687.0	151

The population quota is 173,647 (25,005,200 divided by 144). The resulting redistributions must take place by July 2021[20] for them to be in place in time for the next federal election, due by July 2022.

The first sitting of the House of Representatives following the July 2016 election took place on 31 August 2016,[10] and the three-year term was scheduled to expire on 29 August 2019. Following its timeline, the AEC on 31 August 2017 announced an apportionment determination following the completion of processing of the 2016 census. The determination resulted in a reduction of one seat in South Australia to 10, an increase of one seat in Victoria to 38 and an additional seat in the ACT to 3. The total number of seats in the House of Representatives increased from 150 to 151 at the 2019 federal election.[10][21] The number of seats by States in the House of Representatives arising from the 2017 determination were as follows:

State	Seats	Change
New South Wales	47
Victoria	38	1
Queensland	30
Western Australia	16
South Australia	10	1
Tasmania	5
Australian Capital Territory	3	1
Northern Territory	2
Total	151	1

A draft redistribution in Victoria was released on 6 April 2018, and the final distribution was released on 12 July.[22][23] There were also three scheduled redistributions of electoral boundaries, as seven years had elapsed since the last time these boundaries were reviewed.

On 13 November 2014, the AEC made an apportionment determination that resulted in Western Australia's entitlement increasing from 15 to 16 seats, and New South Wales's decreasing from 48 to 47 seats.[9] The number of seats by States in the House of Representatives arising from the 2014 determination were as follows:[24]

State	Seats	Change
New South Wales	47	1
Victoria	37
Queensland	30
Western Australia	16	1
South Australia	11
Tasmania	5
Australian Capital Territory	2
Northern Territory	2
Total	150

A redistribution of electoral boundaries in New South Wales and Western Australia was undertaken before the 2016 election.[24] The redistribution in New South Wales was announced on 16 October 2015, with the Labor-held Division of Hunter proposed to be abolished.[25] The Division of Charlton was renamed Hunter to preserve the Hunter name used since federation.[4] This effectively meant that the Division of Charlton was abolished and the Division of Hunter was retained.[26] A redistribution also occurred in the Australian Capital Territory, as seven years had elapsed since the last time the ACT's boundaries were reviewed.[27]

The historical apportionment of seats for the various states is:[28][29]

A redistribution of federal electoral divisions in the Australian Capital Territory commenced on 4 September 2017, due to changes in the territory's representation entitlement. The AEC released a proposed redistribution on 6 April 2018, and the final determination on 3 July 2018.[30] The redistribution resulted in the creation of a third ACT electoral division named Bean (notionally fairly safe Labor), after historian Charles Bean.[31][32]

New South Wales did not undergo a redistribution after the 2016 federal election.[33]

On 7 December 2016, the Electoral Commission for the Northern Territory announced the results of its deliberations into the boundaries of Lingiari and Solomon, the two federal electoral divisions in the Northern Territory. New boundaries gazetted from 7 February 2017 will see the remainder of the Litchfield Municipality and parts of Palmerston (the suburbs of Farrar, Johnston, Mitchell, Zuccoli and part of Yarrawonga) transferred from Solomon to Lingiari.[34]

A scheduled redistribution began in Queensland on 6 January 2017, and was finalised on 27 March 2018. Changes were made to the boundaries of 18 of Queensland's 30 electoral divisions, and no division names were changed.[35]

A South Australian seat was abolished due to population changes since the state's last redistribution in 2011. Although South Australia's population was still increasing, faster increases in other states saw a reduction in South Australia's representation from 11 to 10 seats. This was the third time South Australia lost a seat since the 1984 enlargement of the parliament, with Hawker abolished in 1993 and Bonython in 2004.[36][37][38]

The redistribution in South Australia commenced on 4 September 2017. The proposed redistribution report was released on 13 April 2018, and the final determination on 26 June 2018. The AEC abolished the division of Port Adelaide.[39] The hybrid urban-rural seat of Wakefield became the entirely urban seat of Spence, after Catherine Helen Spence.[40][41] The more rural portions of Wakefield transferred to Grey and Barker.[42]

A scheduled redistribution began in Tasmania on 1 September 2016.[43] The determinations were announced on 27 September 2017, involved boundary changes, and the Division of Denison was renamed the Division of Clark.[44]

Western Australia did not undergo a redistribution after the 2016 federal election.[33]

A redistribution of federal electoral divisions in Victoria commenced on 4 September 2017, due to changes in the state's representation entitlement. The determinations were announced on 20 June 2018, and created a 38th electoral division named Fraser (notionally a safe Labor).[45]

Several divisions were also renamed: Batman to Cooper (after William Cooper), McMillan to Monash (after Sir John Monash), Melbourne Ports to Macnamara (after Dame Jean Macnamara) and Murray to Nicholls (after Sir Douglas and Lady Nicholls). A proposal to rename Corangamite to Cox (after swimming instructor May Cox) did not proceed.[46]

The Coalition notionally lost the seat of Dunkley and Corangamite to Labor in the redistribution.[47]