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Gains and losses on the electorate roundabout

The latest population data released today (27 June 2017) by the ABS suggests that, for the next election, the number of divisions in South Australia will reduce by one (from 11 to 10) and the number of divisions in both Victoria and the Australian Capital Territory will increase by one. There will be no change in the number of divisions for any other state or territory.

How does representation entitlement work?

Each state and territory is divided into electoral divisions (or seats) for the House of Representatives. The number of divisions is determined by population and the Australian Constitution.[1]

Under section 46 of the Commonwealth Electoral Act 1918 (the Act), the Electoral Commissioner ascertains the populations of the states and territories from the Australian Statistician the day after the anniversary of the first meeting of a newly elected House of Representatives, provided that the ‘House of Representatives has continued for a period of 12 months’.[2] Section 48 of the Act specifies the manner in which representation entitlements are calculated from these population numbers.[3]

The first meeting of the current House of Representatives took place on 30 August 2016, so on 31 August 2017 the Electoral Commissioner will obtain the latest population numbers published by the Australian Bureau of Statistics (ABS).[4] The population numbers that will be available then are the Estimated Resident Population as at December 2016 which were released today.[5]

What does the new population data show?

The Parliamentary Library has used this data to estimate representation entitlements of the states and territories (see Table below).

These estimates show South Australia’s representation entitlement will reduce by one seat. If South Australia is reduced to 10 seats it will return to the number of seats it had at the 1954 election and continue the decline from its maximum representation of 13 seats (1984, 1987 and 1990 elections).

Victoria had annual growth of 2.4%—the highest of any state or territory—causing its representation quota to increase from 37 to 38.

The Australian Capital Territory had above average annual population growth of 1.7%. With the inclusion of the territories of Jervis Bay and Norfolk Island, the ACT’s original representational estimate would be 2.479; however, with adjustment under s 48 of the Electoral Act, representation is increased to 2.544. Therefore, the ACT’s representation increases from two to three seats (see footnotes to table).

We estimate the size of the 46th Parliament will increase to 151 divisions.[6]

Estimated representation entitlements

Dec 2016
number of
members (a)
Entitlement Change
New South Wales 7 797 791 47.320 47 0
Victoria 6 244 227 37.892 38 +1
Queensland 4 883 739 29.636 30 0
South Australia 1 716 966 10.419 10 -1
Western Australia 2 567 788 15.582 16 0
Tasmania (c) 519 050 3.150 5 0
Six states 23 729 561
Northern Territory 245 048 1.487
Cocos (Keeling) Islands 550 0.003
Christmas Island 1 914 0.012
Margin of error        
Total NT (d) 247 512 1.502 2 0
Australian Capital Territory 406 403 2.466
Jervis Bay 403 0.002
Norfolk Island 1 756 0.011
Margin of error 10 694 0.065    
Total ACT (d) 2.544 3 1
Australia 24 385 635 151 1

Note: For representation entitlement purposes: Jervis Bay and Norfolk Island are included with the Australian Capital Territory; and the Northern Territory includes Cocos (Keeling) Island and Christmas Island. Norfolk Island, Cocos (Keeling) Island or Christmas Island will not be included if they are determined to be entitled to a member of their own.

(a) Derived by dividing the population of a state or territory by a population quota, i.e. the population of the six states divided by twice the number of senators for the six states (144) because s.24 of the Constitution requires there to be ‘as nearly as practicable’ twice as many members as senators. The population quota calculated here is 164 060.
(b) Change over current entitlement.
(c) One of the original (six) states at the establishment of the Commonwealth of Australia. Section 24 of the Constitution entitles each original state to at least five members. 
(d) For the NT and the ACT, if the remainder of their calculated number of members is 0.5 or less then s.48 of the Commonwealth Electoral Act 1918 allows a new calculation to be determined after the addition of a margin of error to their population estimate. If the resultant remainder of the new calculated number of members is greater than 0.5 then an additional member is determined for that Territory. In the Table estimates this is not applicable for the NT, but the ACT entitlement is changed with the addition of the current margin of error, so it is shown.


[1].     Information on the redistribution process can be found on the Australian Electoral Commission website, Redistributions, accessed 27 June 2017.

[2].     Commonwealth Electoral Act 1918, accessed 27 June 2017.

[3].     An initial quota is ascertained by dividing the total population of the six states by twice the number of senators from the six states. A quota for each state and territory is then determined by dividing the population of the state or territory by the initial quota. The resultant figure rounded to the nearest whole number determines the entitlement.

[4].     Norfolk Island population numbers have been provided because, due to the Territories Legislation Amendment Act 2016, it has been included in the Australian Capital Territory since 1 July 2016.

[5].     Australian Bureau of Statistics (ABS), Australian Demographic StatisticsDecember Quarter 2016, cat. no. 3101.0, ABS, Canberra, 2017, Table 8, accessed 27 June 2017.

[6].     The House of Representatives has had 150 seats since the 2001 election.

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Stephen Barber and Christopher Giuliano