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A first-past-the-post election can have a spoiler effect, where people vote strategically for one of the larger parties because their actually preferred party has only a very small chance of winning. Ranked voting system have been proposed to mitigate this effect, in some cases (combined with multi-member constituencies) mimicking proportional representation.

Most elections with proportional representation apply a threshold that is usually within the range of 2–6%. This can also lead to a spoiler effect, as in some elections, large parts of the population voted for parties that failed to reach the threshold and were thus not represented (both Russia 1995 and Turkey 2002 this was more than 40%).

Are there any elections that use party-list proportional representation, but also include an option in which voters can express their 2nd/3rd/4th preferred party lists, to which their vote would be transferred in the event that their preferred party would fail to reach the threshold?

  • "pick your three prefered parties in order of preference ( 1 most, 3 least). if 1 fails to enter the threshold, the vote will be transfered to 2, and if 2 fails, it will be transfered to 3. if 3 also fails, it will be counted as blank" / "mark your prefered parties from 1 to N. ballots where not every party is ranked will be rejected" would kind of sort it. – CptEric Apr 24 '18 at 10:00
  • @CptEric That type of voting is used in Scotland and in police and crime commissioner elections in England, but not for local elections in England. – gerrit Apr 24 '18 at 11:57
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I think Australia's voting system for the senate meets your criteria.

If you vote "above-the-line" you have to put at least six party preferences. Typically the senate elections are for 6 seats per state, so the quota to reach is around 14%. If you party fails to reach the threshold, their votes are transferred to the second preferences, and so on. If the party exceeds a threshold, the excess is transferred to the second preferences but as a fraction of a vote.

Interestingly, the system was recently changed. Before, it was still preferential, but if you voted above-the-line you could only vote for one party and the preferences would be distributed according to a list registered by the party before the election. This led to a gaming of the system, which enabled the Australian Motoring Enthusiasts Party to win senate seat with only 0.51% of the vote. The method works by the so called "micro-parties" agreeing to preference each other ahead of the major and minor parties. Thus, due to the preferential system, if the combined total of their votes exceeds a quota, one of them would be elected. In the election there were 23 micro-parties, so the average vote needed by each of them for the method to work was less than 1%.

Also the optional preferential system used in Queensland, Australia. In this system, you can preference one, many, or all candidates. If your first preference candidate has the fewest votes, the candidate is removed, and your vote will be transferred to your second preference. The process is repeated until two candidates remain, with the winner having over 50%. If you only marked a few candidates, it is possible they won't make the final two and in that case your vote is considered "exhausted".

  • The first few paragraphs are informative, although I think it would be better to make clear that the system being referred to is known in most of the world as PR-STV. I would also point out that PR-STV is similar to party-list PR because voters have the option to vote below the line, which would not be possible in a true party-list system. – Iota May 1 '18 at 21:12
  • I don't think the final paragraph is really relevant, as what it seems to be describing is Ware's method (aka. IRV, aka. the Alternative Vote) which is not in any sense a form of party-list proportional representation. – Iota May 1 '18 at 21:16
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The arbitrary thresholds your refer to are a problem, because they will have a distorting effect on the election result, especially if a large number of voters support minor parties, and therefore have their votes discarded when the final count is done.

It is not (strictly speaking) a party-list voting system, but the method used to elect the Australian Senate operates somewhat like a ranked choice party-list system in practice.

The Senate is elected using PR-STV (proportional representation by means of the single transferable vote).

However electors are permitted to cast an "above the line" vote, which means that the voter can choose to rank the political parties in order of preference rather than choosing between individual candidates.

I gather that, in practice, a large majority of voters choose to vote "above the line" by party rather than by candidate.

https://en.wikipedia.org/wiki/Australian_Senate#Electoral_system

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The term you're looking for is Single Transferrable Vote

When STV is used for single-winner elections, it is equivalent to the instant-runoff voting (alternative vote) method. STV used for multi-winner elections is sometimes called "proportional representation through the single transferable vote", or PR-STV."STV" usually refers to the multi-winner version, as it does in this article. In the United States it is sometimes called choice voting, preferential voting or preference voting ("preferential voting" can also refer to a broader category, ranked voting systems).

This article lists Ireland, Malta, the UK, India, Nepal, Pakistan, Australia, New Zealand, and the US as using this system in at least some elections.

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