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Understanding 3CP trends

June 27, 2022 - 10:00 -- Admin

As the minor party and independent vote has increased, we have seen the voting method used for the House of Representatives take on more complex and difficult to predict features. Nearly every MP has been elected without a majority of the vote, and an independent or minor party made the final count in one sixth of all seats. More broadly, the AEC was not able to call as many races based on the primary vote and two-candidate-preferred vote, with a mathematical chance of the distribution of preferences changing the outcome in about half of all seats.

Most close races typically focus on the two-candidate-preferred (2CP) count, but there have been an increasing number of races where the order of elimination comes into play, with the three-candidate-preferred (3CP) count deciding who makes the final two (and in some cases the 2CP is a foregone conclusion).

Greens candidate Stephen Bates won the seat of Brisbane despite narrowly coming third on primary votes, overtaking Labor and then winning the race with relative ease over the Liberal National Party with the benefit of Labor preferences. There were also questions about the order of elimination in Macnamara and Richmond.

Traditionally the AEC has conducted two-candidate-preferred counts as a matter of course in every seat, starting as soon as possible on election night, but in 2022 they also conducted ad hoc three-candidate-preferred counts in Brisbane and Macnamara which clarified the winner well in advance of a full distribution of preferences.

The AEC has now published the full distributions of preferences for all 151 seats, although unfortunately they are in a user-unfriendly PDF format, not yet in the tidy CSV format available for the 2004-2019 elections. I have produced a spreadsheet with just the percentages for the last three candidates at the second-last round of the count (the 3CP, in other words) which you can download here.

The three-candidate-preferred count will become a more important part of our electoral system, so this blog post is about analysing who makes that count, and how it has changed over time.

First up, let’s look at how the gap between second place and third place has been changing over the last two decades. I originally analysed this gap on primary votes, but actually the 3CP is the crucial round. It accounts for any preference flows from minor candidates, and it’s the actual round which decides who makes it into the top 2. If the 3CP gap between second and third is close, that means a seat can be more marginal and the result less clear.

This first chart shows how many seats have a particular gap at each of the last seven elections.

The mode (the most likely outcome) was in the high 20s back in 2004, and had slowly shifted to the left. You can see an increasing number of seats with a 3CP gap of less than 10%.

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This next chart shows the same data but boiled down to the average and the median, and both have been shrinking steadily, from 25-26% in 2004 to around 15% in 2022.

There are ten seats where the gap between second and third on the 3CP was less than 4%:

  • Maranoa - 0.20%
  • Groom - 0.33%
  • Macnamara - 0.64%
  • Hume - 0.83%
  • Brisbane - 1.66%
  • Mallee - 2.07%
  • Canberra - 2.20%
  • Page - 2.39%
  • Richmond - 2.53%
  • Sydney - 3.06%

Of the 151 seats contested this year, 126 saw no change in the rankings between the primary vote and the 3CP, and four others saw the first- and second-placed candidates swap places, but they still both made the 2CP. In 18 other seats, the fourth-placed candidate on primary votes made it into the 3CP, and in one of those 18 cases they actually made it into the 2CP. There were a further three seats where the second-placed candidate dropped to third place on the 3CP.

Thus there were four seats where the candidates in the 2CP were not the same top two from the primary vote: Brisbane (Greens overtook Labor), Macnamara, Richmond (Coalition overtook the Greens) and Groom (independent Suzie Holt came from fourth place to overtake Labor and One Nation).

Eleven parties made the three-candidate-preferred in 2022, as well as independents (eight if you count the Coalition as a single unit).

  • Coalition - 153
  • Labor - 150
  • Greens - 89
  • Independent - 26
  • One Nation - 20
  • United Australia - 10
  • Lambie Network - 2
  • Katter's Australian - 2
  • Centre Alliance - 1

There were two seats where both Liberal and Nationals made the top three. In Nicholls, they made the top three along with an independent. Nicholls was also the only seat where Labor didn't make the top three. In Durack, the top three was between Labor, Liberal and Nationals.

Exactly one minor party reached the 3CP in 150 out of 151 seats. The only exception was Durack, but if you treat the WA Nationals as a minor party, you have a complete set of 151.

This next chart shows how this has changed over the last two decades.

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The Palmer United Party made the 3CP in almost a third of all seats in 2013, but they went away in 2016.

The Nick Xenophon Team made the top three in all 11 South Australian seats in 2016, and then at the last two elections we've seen an increasing number of independents making that count.

This next chart shows the median percentage at the 3CP point for each of these parties over the last seven elections.

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While the Greens has made the 3CP in fewer seats, their 3CP vote in the remaining seats is going up, which is consistent with the Greens making up a smaller share of a larger non-major party vote. The median percentage for independents in the 3CP has also shot up markedly in 2022, which is consistent with their results.

Finally, I've made a map which I think gives an interesting perspective on the relative strength of the minor parties across the country. The map shows which minor party made the 3CP in each seat. The Greens, One Nation, United Australia and independents have their own colours, while the other parties, all of which only made the 3CP in 1-2 seats in a specific geographic area, are all coloured purple.

If you scroll around, you see plenty of green, but the patches of One Nation orange and UAP yellow in outer suburbia is quite clear.

This is my last blog post for now on the federal election. Stay tuned for some new content on other elections, coming soon.