3 ms·

> if you want the greens or noone, you get exactly what you want Except you don't get no-one, you get one of the two big parties. (Getting no-one would be lik

> if you want the greens or noone, you get exactly what you want Except you don't get no-one, you get one of the two big parties. (Getting no-one would be like "none of the above" winning, which is a supported outcome in some election systems). The best I can do to steelman your argument is to imagine you meant "the greens or anyone", because then, yes, the winner was "anyone", but that's not what a voter necessarily thought they were doing by being "loyal" to the green candidate. Instant-runoff voting (used in practice for counting RCV ballots in the US) actually satisfies the "later-no-harm" criterion[0] of voting systems (unlike Approval Voting), so if a voter knows this fact, they may feel comfortable adding the extra signal of additional preferences to their vote, but otherwise they might be reluctant to, making their vote less effective due to lack of education or misplaced loyalty. You're right that this is a minor problem compared to the extensive flaws in FPTP, but it is a new and avoidable flaw, and it will affect people who might have previously benefited from (the unfairness of) FPTP. I'm not "comparing to a parliamentary system", though, since both presidential and parliamentary systems are compatible with both RCV/IRV and FPTP, and I think everything we've mentioned is equally applicable to individual and non-partisan posts. [0] https://en.wikipedia.org/wiki/Later-no-harm_criterion https://en.wikipedia.org/wiki/Later-no-harm_criterion

ClayShentrup 4y ago
> Instant-runoff voting (used in practice for counting RCV ballots in the US) actually satisfies the "later-no-harm" criterion[0] of voting systems (unlike Approval Voting) This is a flaw for instant runoff voting at a benefit for approval voting. In a nutshell, later no harm means voting for your second can't hurt your first. But it can also mean that your vote for your second can't hurt your third either. Thus if it's more important to target your third than your first, you want to hoist your second favorite into the first position by burying your true favorite. That can never be strategically good with approval voting. https://medium.com/@ClayShentrup/later-no-harm-72c44e145510 https://medium.com/@ClayShentrup/later-no-harm-72c44e145510
- dane-pgp 4y ago
  You're saying that "later no harm means ... your vote for your second can't hurt your third", which seems strange, given that (by definition) it means your vote for your third can't hurt your second. If you're right, then your second and third preferences can't harm the chances of each other, and it seems like this result must generalize such that your Nth can't hurt your Mth, for all N and M. That would mean that every possible vote has no effect on the outcome of the election, which seems like a contradiction. Obviously I'm missing something, but I'm happy to put that down to the complexity and unintuitive outcomes of RCV/IRV, since Approval Voting is a much simpler system to reason about (and implement). I still disagree that Approval's lack of later-no-harm is a feature, though. In practice, what it means is that voters have to think strategically about how well they think the various candidates will do, in order to decide whether they have to "risk" giving an approval to a candidate who they genuinely don't like, but who might be the only chance of preventing a detested candidate from winning.
  - ClayShentrup 4y ago
    i didn't say your 2nd can't hurt your 3rd, but it can't *IF* your 2nd is eliminated before your 1st. which often happens. for instance, a simplified version of what just happened in alaska: 35% peltola begich 33% palin begich 18% begich peltola 14% begich palin -- https://electionscience.org/commentary-analysis/rcv-fools-palin-voters-into-electing-a-progressive-democrat/ https://electionscience.org/commentary-analysis/rcv-fools-pa... begich is eliminated first, even though he's preferred to each of his rivals by a sizable majority. but more notably here, palin is a spoiler. her supporters get peltola—their least favorite. BUT if they insincerely/strategically rank begich in 1st instead of palin, then begich wins. i.e. they get their 2nd choice instead of their 3rd. so they have to LIE ABOUT THEIR FIRST CHOICE in order to prevent the spoiler effect. whereas this is mathematically proven never to happen with approval voting. > I still disagree that Approval's lack of later-no-harm is a feature, though. In practice, what it means is that voters have to think strategically about how well they think the various candidates will do, in order to decide whether they have to "risk" giving an approval to a candidate who they genuinely don't like, but who might be the only chance of preventing a detested candidate from winning. you can't argue about strategic voting because: 1. as i just showed you, IRV/RCV has an even more severe vulnerability to this—you have to strategize about whether to support your FAVORITE, not whether to support your 2nd favorite. 2. approval voting gets better results with strategic voters than IRV does with HONEST voters, so even in the worst case scenario, approval voting is still better. see these VSE calculations by harvard stats PhD jameson quinn. https://electionscience.github.io/vse-sim/VSEbasic/ https://electionscience.github.io/vse-sim/VSEbasic/ my link already discussed all of this quite clearly.

ClayShentrup 4y ago

> Instant-runoff voting (used in practice for counting RCV ballots in the US) actually satisfies the "later-no-harm" criterion[0] of voting systems (unlike Approval Voting) This is a flaw for instant runoff voting at a benefit for approval voting. In a nutshell, later no harm means voting for your second can't hurt your first. But it can also mean that your vote for your second can't hurt your third either. Thus if it's more important to target your third than your first, you want to hoist your second favorite into the first position by burying your true favorite. That can never be strategically good with approval voting. https://medium.com/@ClayShentrup/later-no-harm-72c44e145510 https://medium.com/@ClayShentrup/later-no-harm-72c44e145510

dane-pgp 4y ago
You're saying that "later no harm means ... your vote for your second can't hurt your third", which seems strange, given that (by definition) it means your vote for your third can't hurt your second. If you're right, then your second and third preferences can't harm the chances of each other, and it seems like this result must generalize such that your Nth can't hurt your Mth, for all N and M. That would mean that every possible vote has no effect on the outcome of the election, which seems like a contradiction. Obviously I'm missing something, but I'm happy to put that down to the complexity and unintuitive outcomes of RCV/IRV, since Approval Voting is a much simpler system to reason about (and implement). I still disagree that Approval's lack of later-no-harm is a feature, though. In practice, what it means is that voters have to think strategically about how well they think the various candidates will do, in order to decide whether they have to "risk" giving an approval to a candidate who they genuinely don't like, but who might be the only chance of preventing a detested candidate from winning.
- ClayShentrup 4y ago
  i didn't say your 2nd can't hurt your 3rd, but it can't *IF* your 2nd is eliminated before your 1st. which often happens. for instance, a simplified version of what just happened in alaska: 35% peltola begich 33% palin begich 18% begich peltola 14% begich palin -- https://electionscience.org/commentary-analysis/rcv-fools-palin-voters-into-electing-a-progressive-democrat/ https://electionscience.org/commentary-analysis/rcv-fools-pa... begich is eliminated first, even though he's preferred to each of his rivals by a sizable majority. but more notably here, palin is a spoiler. her supporters get peltola—their least favorite. BUT if they insincerely/strategically rank begich in 1st instead of palin, then begich wins. i.e. they get their 2nd choice instead of their 3rd. so they have to LIE ABOUT THEIR FIRST CHOICE in order to prevent the spoiler effect. whereas this is mathematically proven never to happen with approval voting. > I still disagree that Approval's lack of later-no-harm is a feature, though. In practice, what it means is that voters have to think strategically about how well they think the various candidates will do, in order to decide whether they have to "risk" giving an approval to a candidate who they genuinely don't like, but who might be the only chance of preventing a detested candidate from winning. you can't argue about strategic voting because: 1. as i just showed you, IRV/RCV has an even more severe vulnerability to this—you have to strategize about whether to support your FAVORITE, not whether to support your 2nd favorite. 2. approval voting gets better results with strategic voters than IRV does with HONEST voters, so even in the worst case scenario, approval voting is still better. see these VSE calculations by harvard stats PhD jameson quinn. https://electionscience.github.io/vse-sim/VSEbasic/ https://electionscience.github.io/vse-sim/VSEbasic/ my link already discussed all of this quite clearly.