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>You never lose by getting more votes Yes you can. Basically the scenario is that by gaining votes from other parties, you can change who is eliminated in the

>You never lose by getting more votes Yes you can. Basically the scenario is that by gaining votes from other parties, you can change who is eliminated in the first round, which changes distribution of second round votes. You can argue about how likely this is to happen, but on some level it doesn't matter. If people can't feel absolutely confident that voting for who they actually want won't reduce their vote's impact, many will continue to vote tactically.

danieltillett 11y ago
That is not how the system works for in example Australia. What happens is the votes for the lowest ranked candidate are given to all the second choice candidates and the process repeated until you get a candidate with 50% of the vote. There is no way that placing your preferred candidate first can ever result in your vote not being given in the order you choose. If you prefer candidate X above candidate y then candidate y will never get your vote unless X is eliminated.
- aninhumer 11y ago
  Yes, I understand how IRV works, and indeed I used to believe it was flawless. >There is no way that placing your preferred candidate first can ever result in your vote not being given in the order you choose. No, but it can end up harming your second choice, by eliminating them early, so your vote for them doesn't matter. This is called Favourite Betrayal, and it's a serious problem with IRV: https://www.youtube.com/watch?v=JtKAScORevQ https://www.youtube.com/watch?v=JtKAScORevQ And as a quick worked example, if you have 4 people voting A>B>C, 4 people voting C>B>A and 3 people voting B>A>C, then A wins. If one person voting C>B>A changes their vote to B>C>A, then B wins. So by putting C first, they were harming their second choice B.
  - danieltillett 11y ago
    These type of contrived examples appear to occur rarely in practice. I would love to see some bootstrap simulations on real IRV elections results to see how sensitive IRV is to these pathological outcomes. Most of the time you are only interested in which of the major candidates gets your second choice.
    - aninhumer 11y ago
      I don't know if they're that contrived. The scenario is that you have a closely matched two party system (as most FPTP places do) and a third party which is close in popularity to one of the mainstream ones on first votes, but is not universally supported by the remaining mainstream voters over the other mainstream party. That doesn't just sound plausible, it sounds like exactly the pattern of growth for a third party that you'd expect.

danieltillett 11y ago

That is not how the system works for in example Australia. What happens is the votes for the lowest ranked candidate are given to all the second choice candidates and the process repeated until you get a candidate with 50% of the vote. There is no way that placing your preferred candidate first can ever result in your vote not being given in the order you choose. If you prefer candidate X above candidate y then candidate y will never get your vote unless X is eliminated.

aninhumer 11y ago
Yes, I understand how IRV works, and indeed I used to believe it was flawless. >There is no way that placing your preferred candidate first can ever result in your vote not being given in the order you choose. No, but it can end up harming your second choice, by eliminating them early, so your vote for them doesn't matter. This is called Favourite Betrayal, and it's a serious problem with IRV: https://www.youtube.com/watch?v=JtKAScORevQ https://www.youtube.com/watch?v=JtKAScORevQ And as a quick worked example, if you have 4 people voting A>B>C, 4 people voting C>B>A and 3 people voting B>A>C, then A wins. If one person voting C>B>A changes their vote to B>C>A, then B wins. So by putting C first, they were harming their second choice B.
- danieltillett 11y ago
  These type of contrived examples appear to occur rarely in practice. I would love to see some bootstrap simulations on real IRV elections results to see how sensitive IRV is to these pathological outcomes. Most of the time you are only interested in which of the major candidates gets your second choice.
  - aninhumer 11y ago
    I don't know if they're that contrived. The scenario is that you have a closely matched two party system (as most FPTP places do) and a third party which is close in popularity to one of the mainstream ones on first votes, but is not universally supported by the remaining mainstream voters over the other mainstream party. That doesn't just sound plausible, it sounds like exactly the pattern of growth for a third party that you'd expect.