optional preferential voting

How many NSW contests would have had different results under full preferential voting?

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 OPV can now only be repealed by referendum.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.

I explained more about the political impact of OPV in this post published before the NSW election.

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.)
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The Political Impact of Optional Preferential Voting – NSW 2019 Preference Flows

As mentioned in my previous post, New South Wales is the only Australian jurisdiction that uses optional rather than compulsory or full preferential voting for single member lower house elections. It is also the only state that data enters all lower house ballot papers and publishes the data for outside research.

Optional preferential voting (OPV) means that voters do not have to number a preference for every candidate on the ballot paper. A ballot paper requires only a first preference to be formal. All further preferences are optional.

If during the distribution of preferences, a ballot paper for distribution has no preference for a candidate remaining in the count, the the ballot paper is put aside as having “exhausted” its preferences. Exhausted ballot papers have no direct involvement in determining the winning candidate, but they have an indirect role in altering the winning post a candidate must pass to win. As explained below, OPV works in favour of leading candidates over trailing candidates.

This can be explained by comparing the maths of full versus optional preferential voting.

  • Under full preferential voting, the winning candidate must achieve 50% of the formal vote after the distribution of preferences. The winning post of the votes needed to win is set at the start of the count and does not change.
  • Under optional preferential voting, the winning candidate must receive a majority of the votes remaining in the count, that is the formal vote minus exhausted preferences. The winning post is lowered with each exhausted preference making it easier for the leading candidate to win by making it harder for the second placed candidate to catch and pass the leader.

The chart below shows the two-party preferred preference flows for minor parties and Independents at the 2019 NSW election.

I'll explain the political implications of the above graph inside the post. But if you want more detail of the preferences flows by electorate by candidate, or by party by electorate, you can find all the details in this pdf document I've prepared.
Read More »The Political Impact of Optional Preferential Voting – NSW 2019 Preference Flows

Preference Completion Categories – 2019 NSW Election

New South Wales is the only Australian jurisdiction that uses optional rather than compulsory or full preferential voting for single member lower house elections. It is also the only state that data enters all lower house ballot papers and publishes the data for outside research.

Over the next few days I’ll publish more information on lower house preference flows, but this first post concentrates on preference completion rates.

For this analysis, all ballot papers have been categorised into one of three categories.

  • Single – ballot papers that counted with only a single preference.
  • Full – ballot paper with all squares filled completing a formal sequence of preferences.
  • Partial – formal preferences between 2 and (Max Candidates -1).

Overall 64.3% of ballot papers counted as 1-only votes and had no further preferences. 23.7% of ballot papers counted with all preferences correctly completed, and a further 12.0% had partial preferences. The median number of preferences completed was 1, the average 2.4.

The rate of completion varied substantially by party and also varied from electorate to electorate. This variation in rate is clearly related to published and distributed how-to-vote material. As I don’t have access to the how-to-votes, this post won’t include analysis based on recommendation.

But if you want to see the numbers by electorate by candidate, or by party by electorate, you can find all the details in this pdf document I’ve prepared.

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Candidates, Informal Voting and Optional Preferential Voting

In the final week of parliamentary sittings, Queensland LNP Senator James McGrath tabled the report of the Joint Standing Committee on Electoral Matters (JSCEM’s) inquiry into the conduct of the 2019 Federal election. (You can find the report here.)

One of the controversial proposals in the report, and one opposed by Labor and Green members of JSCEM, was a recommendation to move from full or compulsory preferential voting (CPV) to optional preferential voting (OPV) for House of Representatives elections.

The report provides few arguments in favour of OPV. The recommendation for OPV appears suddenly at the end of a brief discussion on informal voting, in particular noting the impact OPV’s use at NSW elections has on informal voting at Federal elections. Senate McGrath presented a different argument for OPV when tabling the JSCEM report in the Senate, referring to OPV as a measure “to maximise voter choice”.

I’ve written on OPV many time previously, and I would suggest reading this post I wrote in 2013 after a previous suggestion from the Coalition about introducing OPV.

Informal voting will always be higher under compulsory preferential voting because ballot papers with faulty numbering have few options for salvation available. This compares with OPV where ballot papers with incomplete, duplicate or missing numbers, or completed with a single tick or cross, can count for candidates to the extent that a voter’s intent is clear.Read More »Candidates, Informal Voting and Optional Preferential Voting

South Australian Government Proposes Optional Preferential Voting

In proposing that South Australia adopt optional preferential voting for House of Assembly elections, the Marshall government is highlighting democratic principles in favour of making preferences optional. But you don’t have to be cynical to see that in backing principle, the SA Liberal Party is also backing its own self-interest.

Since 1982 there have been 26 South Australian electoral contests where a candidate trailing on first preferences won. Of these, 14 were won by Labor, 11 by Independents or minor party candidates, and just one by the Liberal Party. (Newland in 1989).Read More »South Australian Government Proposes Optional Preferential Voting