2019 Western Australian State Redistribution

The landscape for the next Western Australian election has been finalised this morning with the Electoral Boundaries Commission releasing the new boundaries that will apply at the next election.

With the state’s population growth having slowed since the height of the mining boom, the scale of the changes wrought by the redistribution are much smaller than those produced by the last re-draw in 2015.

Despite population growth being concentrated in Perth and the south-west, the Commission has not repeated its 2015 decision to abolish a rural seat and create a new district in Perth. This means that 38 of the 43 seats in Perth have an above average enrolment.

On paper the boundaries increase the McGowan government’s hold on office, increasing the uniform swing needed for a change of government.

This post was updated, 28 November, with more information and adjusted margins for Hillarys and Joondalup.
My publication on the redistribution for the WA Parliamentary Library is now available at this link.

(Details on all the new boundaries can be found at the WA Electoral Redistribution Commission’s website.)

The Labor Party won 41 seats at the 2017 election, reduced to 40 following the loss of the Darling Range by-election in June 2018. The swing for the McGowan government to lose its majority on the old boundaries had been 5.8%.

Labor’s most marginal seat, Joondalup, looks to have slipped on to the other side of the pendulum on the new boundaries. The new boundaries have boosted Labor’s position in a number of marginal seats the government needs to retain to hold office. (See notes on calculations later in this post to explain the change to the estimated margin for Joondalup.)

On the new boundaries, the uniform swing needed for a change of government increases from 5.8% to 7.9%.

However, there is always variability in swing from seat to seat. Labor achieved a 12.8% swing at the 2017 election, but nine of the seats Labor gained were achieved by swings of more than 16%, the biggest winning swing being 23% in Bunbury.

Some seats won by Labor in 2017 will be easier to defend in 2021 because the formerly well-known Liberal MPs were defeated.

Some Labor MPs defending marginal seats will need to develop a personal vote if they hope to withstand any swing back from Labor’s high point in 2017. Some Labor MPs who won normally Liberal seats in 2017 will find winning the second time round tougher.

Some of the key seat changes are as follows.

  • Balcatta – Safe Labor voting territory in Westminster replaces a less favourable Labor area in Hamersley, boosting Labor MP David Michael’s margin from 5.8% to an estimated 8.0%. Balcatta is a traditional Labor seat that only fell to the Liberal Party for one term on the Barnett government’s landslide re-election in 2013.
  • Bicton – A 10% Liberal seat when created by the 2015 redistribution, Bicton was won narrowly by Labor’s Lisa O’Malley at the 2017 election.  The addition of the last parts of  East Fremantle boost her margin from 2.9% to 3.6%.
  • Burns Beach – a narrow Labor gain in 2017, the new boundaries for Burns Beach include strongly Labor voting Quinns Rocks transferred from Butler, while more evenly divided parts of Joondalup and Iluka have been moved into Joondalup. Labor MP Mark Folkard’s margin increases from 2.5% to an estimated 5.4%.
  • Hillarys – loses strong Liberal voting territory in Sorrento to Carine, replaced by slightly Labor leaning parts of Beldon and Mullaloo. This cuts the margin of Liberal MP Peter Katsambanis from 4.1% to an estimated 0.4%.
  • Jandakot – Parts of Liberal voting Leeming have been transferred to Riverton, boosting the margin of Labor MP Yaz Mubarakai from 1.0% to an estimated 1.8%. Jandakot was one of the seats that fell from the clouds to be won by Labor in 2017 after a swing of 19.3%.
  • Joondalup – Collects Liberal voting territory from Burns Beach while losing Labor voting areas in Beldon and Mullaloo to Carine. These changes virtually wipe out the margin of Labor MP Emily Hamilton. Those changes are enough to turn the 0.6% margin of Labor MP Emily Hamilton into an even closer notional Liberal margin of 0.4%.
  • Kingsley – The addition of Labor voting Hamersley from Balcatta increases the margin of Labor MP Jessica Stojkovski from 0.7% to 1.2%.
  • Landsdale – previously known as Girrawheen, the Labor margin in this seat has been slashed from 16.7% to 9.6%, though it remains a safe Labor seat.
  • Morley – A small boost for Labor’s Amber-Jade Sanderson from 11.4% to 12.3% as the electorate’s eastern boundary moves from the Tonkin Highway to Beechboro Road. A seat that Labor should not have lost to the Liberal Party in 2008.
  • Swan Hills – A reduction in margin from 14.5% to 12.1% for Labor MP Jessica Shaw doesn’t look troublesome, but Swan Hills was won by Labor with a swing on 18% in 2017.
  • Wanneroo – Labor MP Sabine Winton has her margin increased from 7.3% to 8.6%.

Notes on Hillarys and Jondalup

Update added 28 Nov 2019
William Bowe published estimated margins for all seats in July this year when the draft boundaries were released. The analysis can be found on his Pollbludger website. There were only the tiniest differences between the draft boundaries and the final boundaries released yesterday.

Bowe had slightly different margins for Hillarys and Joondalup, estimating that Hillarys slipped narrowly on to the Labor side of the electoral pendulum (my estimates left it as marginal Liberal), and Joondalup remained as a very marginal Labor seat (my estimate was that it became a marginal Liberal seat).

The differences are caused by how polling place catchment areas divided by new electoral boundaries are split between new electorates. I’ll explain how the differences came about, and why I’ve changed my estimate for both seats.

Hillarys – the new boundaries transfer the suburb of Sorrento to Carine. This area contains two polling places, Sorrento Primary School which recorded a 59.2% Liberal two-party preferred vote, and Sacred Heart College which recorded 71.7%. If you transfer both polling places and the related proportion of declaration votes, then the new Hillarys comes out with a tiny Labor majority. However, if you do the full transfer of both polling places, votes transferred comes out at 94% of the electors transferred, which is too high compared to 89% for Hillarys at the last election. For that reason I split the Sacred Heart booth as being closest to the new boundary, which is why my estimates had Hillarys as a Liberal seat. I’ve adjusted the way I divided the polling place and my estimated margin is reduced from 0.6% to 0.4%. Given the seat has a Liberal MP, I am entirely comfortable with this estimate. Small changes to the way you deal with a single polling place can have a significant impact on estimated margins.

Joondalup – The complexity with Joondalup is its new northern boundary. A part of Joondalup was transferred from Burns Beach to Joondalup, as well as the suburb of Iluka. However, there are no polling places in Iluka. There are two polling places on the Burns Beach side of the new boundary, at the Francis Jordan Catholic School in Currambine, and the Bramston Park Community Sporting Facility in Burns Beach. On my initial part transfer of those polling places, Joondalup was calculated as a marginal Liberal seat. Having reviewed my partial transfers, Joondalup ends up with a tiny Labor majority of 0.03%, putting the seat back on the Labor side of the pendulum, where William Bowe had originally estimated it to lie. A result of this change also cuts the Labor margin for Burns Beach from 6.1% to 5.4%.

This new calculation has what I think is a better split of the Burns Beach booths. It also leaves Jondalup on the Labor side of the pendulum, which has an advantage in trying to explain the next election. Seats that are classified by past votes rather than by the party status of the sitting MP are a major source of complaints concerning the ABC’s election results site. If having Joondalup classified as a Labor seat minimises the number of outraged emails about idiots at the ABC who don’t know how to classify seats and analyse elections, then it gets a tick of approval from me.

The above calculations show that all redistributed margins are estimates based on assumptions and calculations. I would say there is always around half-a-percent of fudge factor in redistribution estimates, and with secret ballots, there is always a limit to how accurate you can make estimates.

A Note on Classifying Seats

In the pendulum below, two seats need explanation.

Darling Range was won by the Labor Party at the 2017 election, but won by the Liberal Party at a June 2018 by-election. The Liberal margin from the by-election has been used.

In Geraldton, sitting MP Ian Blayney resigned from the Liberal Party and now sits as a National MP. His seat is shown as National held with the Liberal two-party preferred margin from 2017.

On my calculations, the new boundaries push on to the Liberal side of the political ledger. It is shown on the pendulum with its estimated Liberal margin but highlighted as having a Labor MP. Others have estimated Joondalup as a very marginal Labor seat based on different assumptions about splitting polling places and allocating declaration votes. See notes above on new calculations for Joondalup.

Estimating new margins after a redistribution requires assumptions to be made about splitting polling places and re-allocating postal, pre-poll and absent votes. Such calculations are an inexact science.

The calculations cannot take account of the popularity of sitting members. This is the first redistribution in some time that hasn’t pushed Albany on to the Liberal side of the electoral pendulum, and as all followers of Western Australian politics will know, current Labor MP Peter Watson has defied new margin calculations after every redistribution since he was first elected in 2001.

Electoral Pendulum for the 2021 Western Australian Election

Labor Seats (40) Liberal/National Seats (14/5)
Margin Electorate Margin Electorate
ALP 0.03 Joondalup LIB 0.4 Hillarys
ALP 1.2 Kingsley LIB 0.8 Dawesville
ALP 1.7 Murray-Wellington NAT 1.3 Geraldton (MP changed party)
ALP 1.8 Jandakot LIB 3.5 Darling Range (by-election)
ALP 2.2 Pilbara LIB 4.2 Riverton
ALP 2.3 Kalamunda LIB 5.7 Scarborough
ALP 2.6 Bicton LIB 6.2 Kalgoorlie
ALP 4.0 Mount Lawley LIB 7.2 South Perth
ALP 5.4 Burns Beach LIB 7.8 Bateman
ALP 5.9 Albany LIB 8.0 Nedlands
ALP 7.9 Southern River NAT 10.1 North West Central
ALP 8.0 Balcatta LIB 10.2 Carine
ALP 8.6 Wanneroo LIB 11.7 Churchlands
ALP 9.4 Forrestfield NAT 12.8 Warren-Blackwood
ALP 9.6 Landsdale LIB 14.1 Cottesloe
ALP 10.5 Bunbury LIB 14.6 Vasse
ALP 11.4 Belmont NAT 19.5 Moore
ALP 12.1 Swan Hills NAT 22.2 Central Wheatbelt
ALP 12.3 Morley NAT 25.9 Roe
ALP 12.6 Perth
ALP 12.8 Midland
ALP 13.1 Kimberley
ALP 14.3 Cockburn
ALP 14.7 Collie-Preston
ALP 15.8 Thornlie
ALP 16.6 Baldivis
ALP 16.8 Victoria Park
ALP 17.6 Cannington
ALP 17.7 Willagee
ALP 17.9 Maylands
ALP 18.0 Mandurah
ALP 18.4 West Swan
ALP 20.5 Butler
ALP 20.7 Kwinana
ALP 21.6 Bassendean
ALP 23.0 Fremantle
ALP 23.3 Mirrabooka
ALP 23.5 Rockingham
ALP 23.7 Warnbro
ALP 25.2 Armadale

Summary of Changes for all Districts

Change in Margin Notes on Changes
Old ALP 5.1 Strengthened slightly for Labor with the transfer of the Shire of Jerramungup to Roe
New ALP 5.9
Old ALP 25.2 No change
New ALP 25.2
Old ALP 5.8 Strengthened for Labor with the gain of Westminster from Mirrabooka and loss of Hamersley to Kingsley.
New ALP 8.0
Old ALP 17.9 Loses Bertram and parts of Leda to Kwinana and part of Waikiki to Rockingham. Gains parts of Baldivis east of the Kwinana Freeway from Darling Range.
New ALP 16.6
Old ALP 21.5 Gains Bennett Springs and parts of Caversham from West Swan and Midland. Loses parts of Beechboro and Morley to Morley.
New ALP 21.6
Old LIB 9.5 Gains parts of Kardinya and Murdoch from Willagee.
New LIB 7.8
Old ALP 11.4 No change
New ALP 11.4
Old ALP 2.9 Gains around a thousand voters in East Fremantle from Fremantle.
New ALP 3.6
Old ALP 10.8 Gains around 1,100 voters in Gelorup and areas south of Bunbury from Collie-Preston.
New ALP 10.5
Burns Beach
Old ALP 2.5 Strengthened for Labor as the seat moves north, gaining Quinns Rocks from Butler and loosing parts of Joondalup and Iluka in the south to Joondalup. (Estimated margin adjusted down from 6.1% to 5.4% after reviewing calculations.)
New ALP 5.4
Old ALP 19.4 Loses Quinns Rocks in the south to Burns Beach.
New ALP 20.5
Old ALP 18.1 Loses rest of Wilson to Victoria Park and the balance of the suburb of Riverton to Riverton. Gains part of Wilson from Victoria Park.
New ALP 17.6
Old LIB 9.0 Moves north, gaining Sorrento from Hillarys, losing parts of North Beach and Gwelup to Scarborough in the south.
New LIB 10.2
Central Wheatbelt
Old NAT 22.6 Shifts south losing the Shires of Wongan-Ballidu, Goomalling and Dowerin to Moore, gaining the Shires of Cuballing, Wickepin and Kulin from Roe.
New NAT 22.2
Old LIB 13.2 Moves north, losing parts of City Beach to Cottesloe, gaining parts of Doubleview and Scarborough from Scarborough.
New LIB 11.7
Old ALP 15.9 Moves east of the Kwinana Freeway in gaining Atwell from Kwinana. Loses parts of Spearwood and Munster to Willagee.
New ALP 14.3
Old ALP 14.7 Gains around 2,500 voters in the south of the Shire of Harvey from Murray-Wellington. Loses areas around Gelorup to Bunbury, Balingup to Warren-Blackwood and a smaller area around Capel River to Vasse.
New ALP 14.7
Old LIB 13.3 Gains around 2,000 voters in City Beach from Churchlands.
New LIB 14.1
Darling Range
Old ALP 5.8 Loses Kalamunda and Mundaring Shires in the north, as well as parts of Baldivis and Wellard east of the Kwinana Freeway. The estimated Labor margin rises slightly to 6.0%. However, Darling Range was won by the Liberal Party at a June 2018 by-election and the seat is shown here with its by-election margin.
New LIB 3.5
Old LIB 0.7 Loses Clifton, Herron and Bouvard to Murray-Wellington. Loses part of Dudley Park to Mandurah. (Corrected text)
New LIB 0.8
Old ALP 9.4 No change
New ALP 9.4
Old ALP 23.1 Loses around a thousand voters in the balance of East Fremantle to Bicton.
New ALP 23.0
Old LIB 1.3 Unchanged. MP Ian Blayney has defected from the Liberal to the National Party.
New NAT 1.3
Old LIB 4.1 Moves north, gaining Beldon and Mullaloo from Joondalup, losing Sorrento and its strong Liberal vote to Carine. Estimated margin adjusted down from 0.6% to 0.4% after reviewing calculations.
New LIB 0.4
Old ALP 1.0 Loses parts of Leeming east of Karel Avenue to Riverton.
New ALP 1.8
Old ALP 0.6 Moves north gaining parts of Joondalup and Iluka from Burns Beach, losing Beldon and Mullaloo in the south to Hillarys. See notes on changed calculations above.
New ALP 0.03
Old ALP 2.5 Gains around 2,000 voters in Mundaring and Pickering Brook from Darling Range.
New ALP 2.3
Old LIB 6.2 Unchanged
New LIB 6.2
Old ALP 13.0 Small change gaining Gibson Desert North.
New ALP 13.1
Old ALP 0.7 Gains Hamersley from Balcatta.
New ALP 1.2
Old ALP 18.1 Loses Atwell in the north to Cockburn. Gains Bertram and parts of Leda in the south from Baldivis, and a part of Wellard from Darling Range.
New ALP 20.7
Old ALP 16.7 New name for the former seat of Girrawheen, shifting north and weakening significantly for Labor. Loses the suburbs of Marangaroo and Girrawheen to Mirrabooka. Gains Hocking and Pearsall from Wanneroo and Alexander Heights from Mirrabooka.
New ALP 9.6
Old ALP 18.0 Gains part of Dudley Park from Dawesville. Loses Barragup and Furnissdale to Murray-Wellington. (Corrected text)
New ALP 18.0
Old ALP 17.9 No change
New ALP 17.9
Old ALP 13.0 In the west loses around 1,100 voters in Caversham to Bassendean.
New ALP 12.8
Old ALP 19.2 Loses Westminster to Balcatta, the rest of Ballajura to West Swan and Alexander Heights to Landsdale. Gains Girrawheen and Marangaroo from the former seat of Girrawheen.
New ALP 23.3
Old NAT 18.2 Gains Wongan-Ballidu, Goomalling and Dowerin Shires from Central Wheatbelt. Loses Kalbarri to North West Central. In a two-candidate contest versus the Liberal Party, the National margin increases from 13.9% to 14.8%.
New NAT 19.5
Old ALP 11.4 Eastern boundary moves from the Tonkin Highway to Beechboro Road, gaining around 3,000 voters in parts of Morley and Beechboro from Bassendean.
New ALP 12.3
Mount Lawley
Old ALP 4.0 No change
New ALP 4.0
Old ALP 1.4 Minor boundary changes with neighbouring Mandurah, Dawesville and Collie-Preston.
New ALP 1.7
Old LIB 8.3 Gains West Perth from Perth.
New LIB 8.0
North West Central
Old NAT 9.5 Gains Kalbarri from Moore. New margin adjusted based on 2017 distribution of preferences for North West Central.
New NAT 10.1
Old ALP 11.8 Loses West Perth to Nedlands.
New ALP 12.6
Old ALP 2.3 Small change losing Gibson Desert North to Kimberley.
New ALP 2.2
Old LIB 4.4 Gains the balance of Riverton from Cannington, and parts of Leeming east of Karel Avenue from Jandakot.
New LIB 4.2
Old ALP 23.4 Gains parts of Waikiki from Baldivis.
New ALP 23.5
Old NAT 26.3 Loses Shires of Cuballing, Wickepin and Kulin to Central Wheatbelt, gains Shire of Jerramungup from Albany. In a two-candidate contest versus the Liberal Party, the National margin slips from 14.4% to 13.8%.
New NAT 25.9
Old LIB 5.6 Moves north, gaining parts of Gwelup and North Beach from Carine, losing parts of Doubleview and Scarborough in the south to Churchlands.
New LIB 5.7
South Perth
Old LIB 7.1 Loses part of Kensington to neighbouring Victoria Park. (Corrected text)
New LIB 7.2
Southern River
Old ALP 7.9 No change
New ALP 7.9
Swan Hills
Old ALP 14.5 Loses the southern parts of Aveley and Ellenbrook to West Swan in exchange for more rural areas east of the Swan River around Herne Hill.
New ALP 12.1
Old ALP 15.8 No change
New ALP 15.8
Old LIB 14.7 Gains a small number of voters around Capel River from Collie-Preston.
New LIB 14.6
Victoria Park
Old ALP 16.5 Minor boundary adjustments, gaining part of Kensington from South Perth, losing part of Wilson to Cannington. (Corrected text)
New ALP 16.8
Old ALP 7.3 Loses Hocking and Pearsall to Landsdale, gains Banksia Grove from West Swan.
New ALP 8.6
Old ALP 23.7 No change
New ALP 23.7
Old NAT 13.4 Gains areas around Balingup from Collie-Preston.
New NAT 12.8
West Swan
Old ALP 17.1 Lots of changes, losing Banksia Grove to Wanneroo, Bennett Springs to Bassendean, Herne Hill and areas east of the Swan River to Swan Hills, gaining southern parts of Aveley and Ellenbrook from Swan Hills, and the balance of Ballajura from Mirrabooka.
New ALP 18.4
Old ALP 15.5 Loses parts of Kardinya and Murdoch to Bateman. Gains parts of Spearwood and Munster from Cockburn.
New ALP 17.7

1 thought on “2019 Western Australian State Redistribution”

  1. Just a few errors here plus and couple queries

    Dawesville lost the balance of Dudley park not gained from Mandurah
    Victoria Park gained the balance of Kensington not lost to South Perth similarly it lost the balance of Wilson to Cannington and didn’t gain it.
    I’m not sure the Liberal margin in Riverton decreases with the addition of conservative Leeming to the electorate despite the small balance of Riverton added.
    Surprised that losing the balance of Leeming to Riverton doesn’t push the Labor notional margin up higher than 1.8%

    COMMENT: I get the booth transfers and calculations right by using a mapping system, but have to compose the words looking at the Commission’s comparison maps. I appear to have got the boundary lines and and the striped areas confused a couple of times on the seats you mention. Fixed. On the Riverton point, it may well be the nearest booth in Parkwood is not representative of the bit of Riverton transferred. All these estimates are guestimates to some extent and I think most of the numbers have about 0.5% of error margin. The transfer numbers for Riverton were 656 from Cannington and 2447 from Leeming.

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