Redistributions are held to keep the number of enrolled voters in each seat roughly equal. In Australia, this equal population per seat is possible for a particular state or territory's seats, but not for all seats in the House of Representatives.
Author
Adrian Beaumont
Election Analyst (Psephologist) at The Conversation; and Honorary Associate, School of Mathematics and Statistics, The University of Melbourne
ABC election analyst Antony Green said in June 2023 that all original states are entitled to at least five House seats, so Tasmania has five seats even though its population should only give it three.
Redistributions are needed when the population of a state increases or decreases relative to the overall Australian population, such that the state is entitled to either add a seat, or a seat is removed from that state.
A year after the first sitting of parliament following an election, the electoral commission determines state seat entitlements based on the latest available population data.
In June 2023, the Australian Bureau of Statistics published population estimates nationally and for all states. Green said these population estimates would require the loss of a seat in both Victoria and New South Wales, while Western Australia would gain a seat. The overall size of the House would fall from 151 to 150 seats since the 2022 election.
These changes occurred because, relative to Australia's overall population, Victoria and NSW's population decreased, mainly due to the COVID immigration shutdowns. WA's population increased relative to Australia.
When states are to lose seats, lower-enrolment seats within that state are targeted for axing. States that gain seats have the new seat created in a high-enrolment area. Axing or creating seats causes knock-on effects to existing seats, which either have to absorb the axed seats, or pull back from created seats.
Redistributions also take place in states that haven't had a change in House seat numbers for at least seven years, to correct inequalities in population dispersion within that state. There is currently a redistribution in progress for the Northern Territory, which has had two seats for a long time.
Changes from the Victorian, NSW and WA redistributions
The determination of state seat entitlements began the redistribution process in Victoria, NSW and WA. On May 31, the electoral commission released draft redistributions for Victoria and WA, and on June 14 the NSW draft redistribution was released. I covered the Victorian and WA redistributions on May 31 and the NSW redistribution on June 17.
These redistributions are drafts, and it is expected to take a few more months before they are finalised. Changes can occur from the draft redistributions to the final ones. Until finalisation, redistributions cannot be used at an election.
In Victoria, the Labor-held seat of Higgins was abolished, while the new seat of Bullwinkel was created in WA. In NSW, North Sydney, held by teal independent Kylea Tink, was abolished. This means that unless MPs in abolished seats can win a different seat or become a senator, they will not be in the next parliament.
Using booth data, election analysts are able to estimate new margins for seats after a redistribution. Sometimes this results in a seat currently held by one party becoming a notional seat for another party. For example, a marginal Liberal-held seat may now include strong Labor booths that were previously in another seat, so it becomes a notional Labor seat.
According to estimates from William Bowe (The Poll Bludger), the newly created WA seat of Bullwinkel is notionally Labor by a 52.9-47.1 margin against the Liberals. All other WA seats will be held by their previous party, with the biggest change a 4.7-point lift in Labor's Hasluck margin to 60.7-39.3.
However, I previously wrote that Labor would be worried about a large swing to the Coalition in WA, as WA has been historically weak for Labor but had over a 10% swing to Labor to be Labor's best state at the 2022 federal election. If there is a large swing to the Coalition at the next election, Bullwinkel and Tangney (also on a 52.9-47.1 Labor margin) are vulnerable.
In Victoria, while Labor-held Higgins was abolished, Liberal-held Menzies will be notionally Labor by 50.7-49.3 after Labor gained 1.3 points, and the Liberal-held Deakin lineball at 50.0-50.0 after Labor gained 0.2 points. But Labor's margin in Chisholm was reduced to 52.8-47.2, a 3.6-point swing to the Liberals.
Teal independent-held seats of Goldstein and Kooyong now take in areas that did not have a teal candidate at the previous election. The Poll Bludger's estimates imply that Kooyong (held by Monique Ryan) will be harder for the teal to retain than Goldstein (held by Zoe Daniel).
In NSW, Tink's North Sydney was abolished. The Poll Bludger's estimates say Bennelong was the only change in notional party alignment, with a 1.1% swing to the Liberals barely putting them ahead of Labor. In Bradfield, the Liberal margin over a teal independent was reduced to 52.5-47.5, a 1.8-point swing to a teal. The Liberal-held Hughes swung 3.7 points to Labor, with the Liberals still ahead by 53.3-46.7.
The redistribution's impact on the next election
I don't think the changes to the electoral map will have a major impact on the next election, due by May 2025. If Labor loses, it's likely that anger over the continued high cost of living will be far more important than the redistributions.
Analyst Kevin Bonham, using the draft redistributions, said his seat model would give Labor 79 of the now 150 House of Representatives seats if there was no two-party swing from the 2022 election, which Labor won by 52.1-47.9. This would be a one-seat gain for Labor from the current House.
Assuming no changes to the crossbench, Labor would have an even chance of retaining its majority with a 51.1-48.9 national two-party win, about where polls are now. The Coalition would need a 51.3-48.7 two-party split in its favour to win more seats than Labor, and a 53.4-46.6 split to win a majority.
Adrian Beaumont does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
