Voting system change boosts Labor and Greens in Brisbane City


I posted back in March about the Queensland government’s proposed reforms to local government in that state. The reforms include a bunch of other changes to electoral finance and council procedures, but I focused on two proposed changes: introducing compulsory preferential voting for single-member elections, as well as introducing proportional representation with compulsory preferences for multi-member elections.

It appears that the latter point is not included in the legislation which was introduced earlier this year and was the subject of a parliamentary inquiry, with it being treated as “the subject of further consultation”. This solves the problem of voters being required to number an absurd number of boxes, but it means we’re stuck without any proportional representation in Queensland council elections for now.

The government is proceeding with the other key piece, which would switch from optional preferential voting (OPV) to compulsory preferential voting (CPV) for elections of mayors and for single-member wards (the map of which councils would be covered by this change is included in this post). This echoes the change made to the state electoral system prior to the 2017 state election.

This system change will most likely have the biggest impact in the City of Brisbane, Australia’s biggest and most important local council, where optional preferential voting has seen a lot of Labor and Greens votes exhaust rather than helping the other party, and where the LNP’s large council majority could be under threat.

By my estimate, I think a switch from OPV to CPV would flip three marginal LNP wards to Labor, while bringing about 2.3% closer to control of the council.

To calculate the change in preferences, I looked at how preferences flowed in the nine Brisbane-area electorates at the 2019 federal election. The AEC publishes preference flow data split up based on the voter’s first preference, whereas state election results do not separate preferences by first preference. About 83% of Greens preferences flowed to Labor ahead of the LNP in these seats.

Most preferences flowing in Brisbane City in 2016 were from the Greens. Only four candidates outside of Labor, LNP or the Greens ran for a council seat in Brisbane in 2016 (in four different wards). The redistribution spread those voters’ votes over nine out of 26 wards, but in most wards preferences would just flow from the Greens.

I assumed a preference flow of 80% to Labor for Greens voters, and 50% to Labor for the small number of independent or other minor party voters. There were four wards where the Greens outpolled Labor, and in these wards I assumed an equivalent preference flow of 80% from Labor to the Greens.

After applying these preference flows, this is how the margins for each ward changed:

WardPartyOPV old boundariesOPV new boundariesCPV new boundaries
Bracken RidgeLNP60.6%59.6%57.4%
Forest LakeALP55.3%55.4%57.3%
Holland ParkLNP54.8%54.0%52.0%
PaddingtonLNP vs GRN55.8%55.6%53.3%
PullenvaleLNP vs GRN68.1%68.0%64.0%
TennysonIND vs ALP76.3%73.3%73.1%
The GabbaGRN vs LNP55.0%56.8%58.2%
The GapLNP55.7%54.5%52.6%
Walter TaylorLNP vs GRN66.5%65.7%63.1%

The voting system change has a much bigger impact than the redistribution. Three wards flip to Labor: Coorparoo, Doboy and Northgate. Coorparoo comes out with a 2PP of 50.02% for Labor.

Labor also gets closer to winning a majority overall, or at least depriving the LNP of a majority. There are currently two members of the crossbench, and the Greens are close enough in Paddington to factor that into swing estimates. The following table shows the swings needed to achieve changes in who holds the majority on council.

ScenarioOPV old boundariesOPV new boundariesCPV new boundaries
LNP lose majority5.7%5.6%3.3%
ALP + GRN gain majority8.0%7.5%5.2%
ALP gain majority8.3%8.9%6.5%
Lord mayoralty flip9.5%9.5%7.7%

The uniform swing required for the LNP to lose their majority, for Labor and the Greens to win a majority between them, or for Labor to win a majority in their own right, all reduce by 2.3-2.4% with a change to the voting system. The swing needed for Labor to win the lord mayoralty drops by 1.8%.

All of a sudden the swing needed for the LNP to lose complete control looks quite achievable, at 3.3%. This would require to lose six wards. Three of these are wards where Labor would likely be leading under CPV without any additional swing, plus Holland Park, the Gap and Paddington (where the Greens are the main challenger). Even a 5.2% swing to give Labor and the Greens a combined majority doesn’t seem out of the question.

We don’t have any polling for the Brisbane City race, so we can’t assess whether such a swing is possible. Labor will have been out of power in City Hall for sixteen years by the time of the election next March, so I could imagine a change in the voting system being the impetus for a more serious threat to LNP control, and potentially a change in Brisbane.

Finally, this map shows the wards of Brisbane, coloured according to who would win under CPV, with the wards flipping to Labor marked in pink.

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  1. Are Greens/ALP voters more likely to already give preferences. If so, would that also make them less likely to vote informally first time after the change?

  2. @Jonathan D
    Yes, to the first bit. The LNP actively run a campaign against preferencing (often with black and white signs that have tiny authorisations), and Labor and the Greens do the opposite.

    For the 2nd bit I’d expect so but to a limited extent since the LNP will change their material and LNP voters are more likely to follow that generally speaking.

  3. Looking at this mornings Courier Mail State Poll they had better start training their voters because every vote will count.
    Jackie Trad is dragging down ALP State Government and no one knows who Lord Mayoral Candidate is or will be?
    Is Greens Councillor Sri going to run for Lord Mayor or is the risk of losing his sinecure just too great?

  4. I imagine the Greens strategy for Council will be fairly similar to last time – fly the flag in every ward, go hard in the several they could win, run a noisy big-target Mayoral campaign to push the agenda forward.

    Sri is recontesting the Gabba, and their Paddington award candidate was announced this week. I don’t know of any others yet.


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