Preferences Explained

Every time an election comes around I notice that lots of people have a poor understanding of how preferences work in Australian federal elections. I’ve written about them before but have decided to bring the blog back to life with a new post explaining how preferences work and tackling some common misconceptions.

The first part is an explanation of the basics of preferential voting without taking a position on who to vote for, but the latter part is mostly about why people who like the Greens should vote for them. If you don’t like the Greens then fine, don’t vote for them, the basic advice still applies regardless of who you want to vote for – preference all candidates in the order in which you like them.

Comments on preferential voting are welcome but this post isn’t for discussing the relative merits of the parties or candidates so such comments will be moderated.

Why have preferences at all?
For the simple reason that it is more democratic and gives a better representation of the electorate’s wishes than first past the post. Now there are all sorts of other changes which people argue for such as proportional representation or multi member electorates and so on, but if you fix all other features of our electoral system and just ask whether it is better with or without preferences then it is undoubtedly better. The shortcomings of first past the post are clearest in the situation where there are similar candidates which split the vote. Imagine that in an election nice candidate A is supported by 35%, nice candidate B by 25% and nasty candidate by 40%. In first past the post the nasty candidate wins, even though 60% of the electorate prefer nice candidates. A fairer system is to eliminate the least popular candidate and then compare those that remain. In some systems this is done by having run-off elections, so they run a whole new election with just the two most popular, with preferential voting it is essentially the same thing but all done at once so you don’t need to organise more than one poll. Nice candidate B is eliminated from the count, and their next preferences are allocated. Some opponents of preferential voting try to claim that this is unfair because those people get two votes, but from that perspective, everyone got two votes, it’s just that the supporters of the two leading candidates were able to vote for their favourite both times.

How do preferences work in the House of Representatives?

The House of Representatives (HoR) or lower house is where Government is formed. It consists of representatives of local electorates across Australia. When you vote, one of the ballot papers is for the HoR candidates in your local electorate. Typically you will have somewhere between 3 and 10 candidates in your electorate – it depends on how many people nominate for it. To vote you just number all of the candidates in the order that you like them. All of the first preferences are counted. The candidate with the fewest votes is eliminated and their second preferences are allocated at full value. This process is repeated until a candidate gets more than 50% of the vote.

 How do preferences work in the Senate? 
The senate, or upper house, consists of representatives from each state and territory. At a regular election half the senate is up for election, which means 6 senators from each state (also the 2 from each territory as well). The voting system is different to allow for multiple members to be elected, but also uses preferences for the same reasons as for the HoR. In the lower house with 1 person being elected, they need 50% plus 1 vote, which is 1/(1+1)*100% + 1. If you wanted to elect 2 people you would expect the required amount to be approximately 33% + 1 vote which is 1/(2+1)*100% + 1. For an election to elect 6 candidates the quota is 1/(6+1)*100% + 1 which is about 14%.

There is an added complication here, a candidate can get in excess of a surplus, to take an extreme example, suppose 90% of people likes one particular candidate, then they would be elected easily, but it wouldn’t be fair to then elect 5 other candidates from what just 10% of the electorate want. As a result, the surplus is redistributed. One way you could do it would be to just use up enough votes for a quota and then allocate the remaining ones to their second preference, but this is rather arbitrary so instead all of them count for their next preference but at a reduced value so that the total number of votes left after electing the first candidate is the total minus 1 quota. For example, suppose you had 100 people and a quota was 14. Let’s say 30 vote for candidate A, so we want to allocate 14 votes to elect them, and have 16 left over that go towards other candidates, so we keep all 30 votes in but now they each have a value of 16/30 each, so the total number of votes in the count are the 70 who voted for someone else plus 30 votes at a value of 16/30, which is 70+30*(16/30) = 86 = 100 minus a quota of 14.

So anyone with over a quota is elected first and their surplus distributed. At the end of this, if there are not yet 6 elected, the procedure is similar to the lower house, you eliminate the least popular and distribute their preferences. You do this until someone else gets over a quota, and if all the spots aren’t filled yet you distribute their surplus and so on until 6 candidates have been elected.

What this means in practice is basically the same as in the HoR, the best approach is to number the candidates in the order in which you like them, preferential voting means you don’t have to make judgements on who is likely to win or not, if your top preferences get eliminated your vote still counts.

Above the line voting

Since there are a large number of candidates in a typical Senate election, meaning a lot of boxes to number, above the line voting was brought in, the justification being to cut down on informal voting. This means that rather than number all of the candidates yourself, you number a single box labelled by party, and your preferences are distributed according to a ticket lodged with the AEC by the party. It is important to realise that these are not secret, they are published online before the election (here and you can ask the officials to view a copy at the polling place. The problem is that many people vote above the line without knowing how the preferences are being directed and then are not necessarily happy with the outcome. This is easily avoided, view preference tickets, if you agree with the one for the party you want to vote for then you can vote above the line, if not then vote below the line, or ignore the tickets entirely and vote below the line.

For the 2013 election some things to be aware of are that the preference allocations of the Wikileaks party have been very controversial, in some states they have preferences right wing parties quite highly, and in WA their preferences could help elect a National Party rather than Greens Senator Scott Ludlam who has been the most outspoken parliamentarian on the issues that they are campaigning on. Here in South Australia preferences from independent Nick Xenaphon go to Labor and Liberal.

So What Does All This Mean For How I Vote?

I agree with the advice usually given by ABC psephologist Antony Green – just vote for the candidates in the order in which you like them. In particular this means there is no need to worry about where your preferences are going – if you number them yourself then nobody can change where your preferences go, preference deals will mean nothing for your vote. It also means don’t worry about who has a realistic chance or not, just vote for who you like, in a preferential system there is no “wasted vote”. Also make sure you do number all of the candidates to make it a formal vote, an informal vote really is a waste.

But if I vote for a minor party does that risk letting the major party I don’t like winning?

No. To make it clearer, consider a specific example, you want to vote Green but don’t want it to let the Liberals win. If the Liberals win then at some stage in the count they achieve over 50% of the votes, let’s say 51% for the sake of argument. Then at this point your vote is with the other 49%, which includes everyone who preferenced Labor above Liberal. Even if you and every other Green voter who doesn’t want the Liberals to win were to change their number 1 to Labor it would not change any of the votes in the 51% who have put Liberals above Labor, so they still win.

There are some complicated scenarios where a change could affect the outcome, these usually involve 3 or more candidates who are very close, but without knowing what everyone else would do there is no real way of predicting the outcome, you are best off voting for who you like best. (There is in fact a mathematical theorem which essentially says that no voting system can avoid these sorts of problems, so it is not a particular weakness of our system).

What’s the point of voting for a candidate who won’t win anyway?

Your first preference is important, it determines the allocation of public funding. If you vote 1 for someone who isn’t really your favourite then you are denying funds to your favoured candidate and giving them to someone else. Also, a first preference for one candidate that goes on to help another candidate win sends a message to the winning candidate about what you think. For example Labor will pay more attention to issues championed by the Greens if they are elected on Greens preferences. Also if you do have a favourite candidate or party who are not likely to win, then if you don’t vote for them then they never will be likely to win. In 2001 the Greens got 15% of 1st preference votes in the seat of Melbourne. In 2010 the Greens won the seat. If the 15% in 2001 hadn’t bothered then it may never have been winnable. In 2010 the Greens got over 15% in many seats, including Mayo and Port Adelaide in South Australia.

I’m Going To Vote Greens In The Senate but not the lower house.

The Greens campaign is focused on the senate since these are where the most likely wins are, but given the discussion above, if you like the Greens then why not give them your lower house vote as well, you still get to have your say with your preference but you get even more of a say with your first vote and help to potentially make your seat winnable in the future.

I’m going to vote informal because my vote will only end up with one of the major parties.

Congratulations, you’ve just helped to maintain the power of the major parties, i.e. you’ve achieved exactly the opposite of what you wanted. If your vote ends up counting for one of the major parties then it means that everyone you like better has been eliminated from the count because the majority of other people did vote for the major parties. Your vote is not making them more likely to win at this point, everyone else voting for them has already done that, your vote is just expressing a preference between them. It is not saying you like them or giving approval for their policies, it is just allowing you to still have a say over who gets elected even though your preferred candidates did not get enough votes to stay in the count. If your vote was informal they would still get elected but the parties or candidates you do actually like lose funding and lose the chance to have be in a more winnable position in the future. Simplistically it seems like you’re denying something from the major parties, but you aren’t really, you are just hurting the party you like. If you cast a formal vote you are helping the party you like and hurting the majors even if your vote goes to them eventually, because your vote is helping to threaten the duopoly. What they really fear is other candidates getting elected. This happened in places like Melbourne, Denison and New England precisely because people cast formal votes for candidates not from the major parties. An informal vote will not change anything, a vote for a candidate you like has a chance to, even if they don’t get elected this time. Just to be clear, preferential voting in no way favours the major parties, in fact without it there would be much less chance of anyone ever being elected since people would be forced to consider whether it is worth voting for someone else they suspect unlikely to win and giving up their say on who actually wins. If you don’t like the major parties the only way to beat them is to elect other candidates, this may mean voting for candidates who aren’t likely to win this time but otherwise there will never be anyone able to build up enough of a vote to beat them in the future.


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  1. […] involving a minimum required number of preferences. OPV is used in some state elections. In a previous post I described why I think preferential voting is better than first past the post (FPP). OPV lies in […]

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