Unlike the Commonwealth and every other mainland state, NSW uses optional preferential voting (OPV) to elect its lower house of parliament. OPV was adopted by the Wran Labor government in 1980, the only state where a Labor government implemented what at the time was party policy. The Whitlam government tried and failed to implement OPV for Federal elections.
Labor’s embrace of OPV followed the Labor Party’s experience with losing seats to the Coalition on DLP preferences between 1955 and 1972. There was also a desire to make it harder for the Coalition to win seats where both parties nominated candidates.
The Wran government not only introduced OPV, it entrenched it in the state’s Constitution. OPV can now only be repealed by referendum. I doubt that a referendum to repeal OPV would pass.
Labor’s hope for advantage from OPV has failed to live up to expectations. The Coalition has largely abandoned three-cornered contests to avoid losing seats. The emergence and growth of the Greens as a left-wing competitor has cut into Labor’s first preference vote and left the party more reliant on preferences to win seats. Labor regularly comes from behind to win at Federal elections under full preferential voting, but come-from-behind wins are harder under OPV at NSW state elections.
At recent NSW elections it has been the Coalition advocating ‘Just Vote 1’ and the Labor Party encouraging voters to complete more preferences.
Inside this post I’ll look at the results of the 2023 election and the seats where preferences determined the winner. Many seats had preference distributed, but only six seats saw preferences change the result by allowing a trailing candidate to win.
Using preference flows from last year’s Federal election where full preferences were required, I look at several state seats where there might have been a different result had full rather than optional preferential voting been used.
My conclusion is the Liberal Party probably won four three extra seats due to OPV, two at the expense of Independents (Pittwater, Willoughby), and two at the expense of Labor (Ryde, Terrigal). (A few people are arguing that Willoughby should not be included in this list. They have a reasonable argument. When the result is final it may just be a matter of the result narrowing substantially rather than changing.)
Seats Decided by Preferences
Around half of all seats at the NSW election required at least some preferences to be distributed before one candidate achieved majority vote. But in assessing the influence of preferences, you need to draw a distinction between seats where preferences are distributed, and those where preferences decided the result.
In political science literature, where preferences decided a contest is defined as where the candidate leading on first preferences did not win. Instead, a trailing candidate passed the primary vote leader to win on the transfer of votes through preferences.
Based on what are still incomplete counts, there are six districts with trailing candidate winners where preferences decided the outcome. These seats, with first preference percentages for the top two candidates, are –
East Hills – first preferences Liberal 44.0%, Labor 43.8%, Labor trailing by 0.2% but going on to win with 51.4% after preferences. Preferences are splitting around 16% to Liberal 41% Labor and 43% exhausting.
Monaro – first preferences National 39.5%, Labor 38.5%, Labor trailing by 1.0% before winning with 52.2% after preferences. Preferences are splitting roughly 16% National, 38% Labor and 46% exhausting.
Penrith – first preferences Liberal 38.7%, Labor 38.4%, Labor trail by 0.3% and go on to win with 51.4%. Preferences are splitting roughly 16% Liberal, 29% Labor and 55% exhausting. One Nation polled 8.2% and appears to have a high rate of exhaustion, but Labor was also disadvantaged by missing out on exhausted Green preferences.
South Coast – first preferences Liberal 35.1%, Labor 34.0%, Labor trail by 1.1% but go on to win with 53.3%. Preferences split roughly 12% to Liberal, 35% Labor and 53% exhausting. A very high 15.4% primary vote for the Greens aided Labor.
Wakehurst – first preferences Liberal 37.2%, Independent Michael Regan 36.2%, Regan trail by 1.0% but goes on to win with 54.7% after preferences. Preferences split roughly 11% Liberal, 46% Regan and 43% exhausting.
Wollondilly – first preferences Liberal 34.1%, Independent Judy Hannan 26.9%, Hannan trails by 7.2% but goes on to win with 51.4% after preferences. Preferences split roughly 14% Liberal, 37% Hannan and 49% exhausted.
The only seat currently undecided is Ryde. If Labor wins, it will be a seventh trailing win. Current first preference counts are Liberal 45.4%, Labor 39.3%, a first preference lead of 6.3 percentage points. At the moment preferences from the Greens and two other minor parties are splitting around 12% to Liberal, 52% Labor and 36% exhausting.
Seats that might have had different results with full preferential voting
To assess the possible impact of full preferential voting, I have used preference flows from the 2022 Federal election in the Federal seat that overlaps the local state seats. With several lower polling parties I have used the parties overall preference flow for the state where a local flow was not available.
The paragraphs below highlight eight seats where there was a significant difference between the state result and a possible full preferential voting margin. On my estimates, the Liberal Party won four more seats under OPV than it would have under full preferential voting. Two of the extra seats could have been lost to Labor (Ryde, Terrigal) and two to Independents (Pittwater, Willoughby).
In all the examples below, there was a much larger gap between the first and second placed candidates than in the seats listed above where trailing candidates won. OPV makes it harder for a trailing candidate to win for two reasons. First, the trailing candidate misses out on preferences it would have received under full preferential voting. Second, a big gap on first preferences means that exhausted preferences lower the winning post by diminishing the number of votes remaining in the count, leaving less room for the second placed candidate to catch and pass the leader.
Pittwater (*** CHANGED ***)
State result currently Liberal 51.0%, Independent Jacqui Scruby 49.0%. Based on Federal preference flows in the local seat of Mackellar, the result would be reversed under full preferential voting with the Liberal two-candidate result reduced to 49.3%. The first preferences are Liberal 44.9%, Scuby 36.0%, a lead of 8.9%, Labor 10.1% and Greens 6.6%. State preference flows are 12% to Liberal, 52% to Scruby and 36% exhausting. In Mackellar last May, Labor preferences flowed 79.5% to the Independent and Green preferences 82.6%. At the state election Scruby missed out on these strong preference flows.
Ryde (*** CHANGED ***)
(Based on current count where the Liberal Party are very narrowly ahead) State Margin Liberal 50.2%, Estimated Federal result based on Bennelong preference flows, Liberal 49.4%. First preferences are Liberal 45.5%, Labor 39.1%, a lead of 6.4%, Greens 10.5% and two others 5.0% in total. Current state preference flows are to Liberal 12%, Labor 52%, exhausted 36%. In Bennelong at the Federal election, Green preference flowed 83% to Labor.
Terrigal (*** CHANGED ***)
Liberal state result Liberal 51.4%, estimated Federal result 49.5%. First preferences Liberal 46.7%, Labor 39.4%, a lead of 7.3%, Greens 9.2%, Sustainable Australia 4.6%. State preference flows Liberal 13%, Labor 50%, 37% exhausted. At the Federal election Green preferences flowed 87% to Labor and the loss of Green preference flows to Labor under OPV has allowed the Liberal Party to stay ahead.
Willoughby (*** CHANGED ***)
State result Liberal 52.6% versus Independent Larissa Penn 47.4%. Estimated Federal result would see a narrow Liberal loss with 49.8%. First preferences are Liberal 43.8%, Penn 26.9%, a gap of 16.9 percentage points, Labor 19.8% and Greens 7.6%. Current state preference are 10% to Liberal, 52% to Penn and 38% exhausted. In North Sydney at the Federal election the flows were Labor 81% to Independent, Greens 85%. Exhausted preferences prevented Larissa Penn from closing the Liberal lead on first preferences.
COMMENT: As has been pointed out to me in comments, the count is not complete in Willoughby so it may in the end be a case of the result narrowing rather than changing. I have also been reminded of a post I did on preference flows in Hawthorn at the Victorian state election where the flows of Labor and Green preferences to a lower profile ‘teal’ independent were weaker than at the preceding Federal election. Whether the Willoughby result changes or just narrows, the result demomstrates the impact of optional preferential voting.
Balmain (***Special case ***)
The state first preference result was Greens 40.5%, Labor 37.1%, Liberal third 19.2%. As elections over the last decade have shown, Liberal preference strongly follow the recommendation made by the party on its how-to-vote material. On the above first preference votes, under full preferential voting Balmain would have been won by the party the Liberal Party tactically chose to direct preferences towards. In Balmain 65% of preferences exhausted reflecting the Liberal Party choosing not to recommend preferences.
Drummoyne (*** Narrowed ***)
State result Liberal 51.5%. Based on preference flows in Reid, the estimated Liberal result would be 50.1%. On first preferences the Liberals lead 47.7% to 39.3% for Labor, a lead of 5.5%. The Greens polled 9.6% and Sustainable Australia 3.4%. State preference flows are 11% to Liberal, 57% Labor and 32% exhausted, a low rate of exhaustion for a state seat. Labor received 87% of Green preferences in Reid, so in Drummoyne the Labor Party has missed out on those Green flows, and the exhaustion rate has aided the Liberal candidate with the higher first preference vote.
Goulburn (*** Narrowed ***)
State result Liberal 51.3%. Based on preference flows in Hume, the estimated Liberal result would be 50.6%. On first preferences the Liberals lead 41.1% to 35.6% for Labor, a lead of 5.5%. The SFF polled a very high 13.9%, Greens 6.9% and Sustainable Australia 3.0%. State preference flows are 20% to Liberal, 34% Labor and 46% exhausted. Labor received 82% of Green preferences in Hume while SFF preferences flowed 53.9% to Liberal. The exhaustion rate here does more harm to the Liberal vote as it deprives the Liberals of the SFF preferences on a very high primary vote. Given the size of the SFF vote, it is hard to know how it would have played out under full preferential voting.
Manly (*** Narrowed ***)
State result Liberal 54.7%, Independent Joeline Hackman 45.3%. Based on preference flows in Warringah, the estimated margin would be Liberal 51.7%. First preferences were Liberal 45.3%, Independent 27.5%, a lead of 17.8%. Labor polled 12.7%, Greens 8.6% and there is 5.9% with three other candidates. Preferences are splitting 12% to Liberal, 46% to Independent and 42% exhausting. At the Federal election preferences to the Independent were 82% from Labor and 87% from the Greens
Oatley (*** Narrowed ***)
State result Liberal 51.3%. Based on preference flows in Banks the result would be much closer but hard to estimate. First preferences were Liberal 45.8%, Labor 39.5%, first preference gap 6.3%, Greens 6.0%, Independent Natalie Ward 5.3% and Sustainable Australia 3.3%. Preferences are splitting 15% to Liberal, 45% Labor and 40% exhausting. Green preferences in Banks at the Federal election were 83% to Labor. Hard to assess because of the Independent but the first preferences in Oatley were close enough for full preferential voting to turn around the result.
North Shore (*** Narrowed ***)
State result Liberal 55.8%, Independent Helen Conway 44.2%. Estimated Federal result based on North Sydney preference flows, Liberal 51.8%. State first preferences are Liberal 44.7%, Conway 22.5%, a gap of 22.2 percentage points, Labor 16.8%, Greens 10.5%. Current state preference flows Liberal 10%, Conway 47%, exhausted 43%. Federal preference flows were Labor 81% to Independent and Greens 85%. The Liberal first preference vote might have been to high to be caught on preferences, but the weaker flows of Labor and Green preferences as well as the weighting boost from exhausted preferences aided the Liberal Party.
Tweed (*** Narrowed ***)
State result National 53.9%, estimated Federal result 50.1%. First preferences National 44.4%, Labor 31.1%, a gap of 13.3 percentage points, Greens 11.5%, 13.0% split across Legalise Cannabis, Sustainable Australia and Animal Justice. State preference flows National 14.0%, Labor 40%, exhausted 46%. In Richmond at the Federal election Green preferences flowed 88% to Labor, and very strong preference flows were needed for Labor to win Tweed given the Nationals began the count well ahead with 44.4%.