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Why is Instant Runoff Voting the worst possible voting method?

by _AzMoo 5y ago

antognini 5y ago
"Worst possible" might be a bit strong, but an important property that a voting system should have is that it finds the Condorcet winner if one exists. The Condorcet winner is the candidate who beats every other candidate in a head-to-head election. IRV is not guaranteed to find a Condorcet winner. The problem with IRV is that you can have a candidate who is everyone's second choice, but then loses out on the first ballot because too few people ranked them first.
- slownews45 5y ago
  I've been voting RCV and I've yet to see this actually occur in practice. The candidates who are marketing themselves so well that they are second on almost everyone's ballot (in a 13 person race!) are generally FIRST on a fair number (relative to all 13 folks).
  - obelos 5y ago
    This is what happened in Burlington, VT that prompted them to repeal IRV/RCV: https://electionscience.org/library/irv-and-core-support/ https://electionscience.org/library/irv-and-core-support/
    - slownews45 5y ago
      Fantastic. Thanks for link. Would screening for a condorcet winner (beats all winner) FIRST then proceeding to RCV address this concern sufficiently? Ballot completion would remain unchanged.
throw_away 5y ago
Worst possible ranked choice alternative, not worst possible voting method (i.e., still better than FPTP, but not without its weaknesses). Frustrating as there are more straightforward, and objectively better mechanisms which are ignored in favor of IRV. It's hard not to feel conspiratorial that maybe the Powers That Be want worse voting mechanisms. This page is a good explainer of IRV's weaknesses and shows some of the alternatives: https://ncase.me/ballot/ https://ncase.me/ballot/
- dane-pgp 5y ago
  > not worst possible voting method Since you mention it, let me offer a candidate for "worst possible voting method (that has actually been used in a democracy)", namely "plurality-At-Large".[0] It basically takes the worst properties of FPTP and extends them to an entire governing body, allowing a party with less than 50% support to win 100% of the seats (by design). Fortunately it has been mostly abandoned in the US thanks to the Voting Rights Act and subsequent SCOTUS decisions. [0] https://www.nonprofitvote.org/the-bias-of-at-large-elections-how-it-works/ https://www.nonprofitvote.org/the-bias-of-at-large-elections...
  - dragonwriter 5y ago
    > Fortunately it has been mostly abandoned in the US thanks to the Voting Rights Act and subsequent SCOTUS decisions. A close variant (vote for up to N, top N win, at large) is used in a lot of local elections still; all multimember district methods are banned in House elections specifically to prevent plurality at large from being used there. (Though the Senate uses temporally-segregated two-seat plurality at large in every state.)
    - dragonwriter 5y ago
      > (Though the Senate uses temporally-segregated two-seat plurality at large in every state.) Correction: it uses either that or similarly segregated majority/runoff, varying by state. Majority/runoff and plurality are similar FPTP variants, but majority/runoff is slightly less bad.
dragonwriter 5y ago
A succinct version (others have linked more detailed, largely outcome-oriented analyses, which are also valid and important) is that, of seriously-considered ranked-ballots methods, it both throws out the most information from the ballots and uses information rather unequally across ballots, attempting to simulate FPTP elections with narrower candidate pools until you get a majority winner.
elihu 5y ago
One of it's big downsides is that you can, in some cases, cause a candidate to lose by ranking them too highly. In voting-theory terminology, it fails the monotonicity criterion. In at least that one respect it's worse than first-past-the-post. (I mean, imagine if people could say "Gore would have won in 2000 if only a few less people had voted for him". That sounds nonsensical, but that's how IRV works sometimes.) Wikipedia has an example: https://en.wikipedia.org/wiki/Monotonicity_criterion#Instant-runoff_voting_and_the_two-round_system_are_not_monotonic https://en.wikipedia.org/wiki/Monotonicity_criterion#Instant... I think first-past-the-post and IRV are both bad voting systems that are unsuitable for real-world use in elections with more than 2 candidates. Approval voting is simpler than IRV and (as far as I know) it isn't worse than FPTP in any way, so I think we should push for that.
- asteroidbelt 5y ago
  > Approval voting is simpler than IRV and (as far as I know) it isn't worse than FPTP in any way FPTP might be better than approval voting, because approval voting favors weak moderate candidates with no agenda. With FPTP the people alternate lefts and rights and the system develops. With moderate candidates the system may stop progressing: no reforms, no bugfixes.
  - elihu 5y ago
    If the voting public prefers a weak moderate candidate with no agenda, then that's the candidate that should win. I think weak moderates usually flop, though, if there's no particularly compelling reason for people to want that person to be president. The way I look at is that it's a kind of relief valve. If both major parties (assuming there are two, maybe there'll be more...) nominate not-so-great candidates, then the voters have an option to elect someone like Tom Hanks. I mean, I would have voted for Tom Hank in 2016 if I had an approval voting ballot and he was one of the options.
    - asteroidbelt 5y ago
      > If the voting public prefers a weak moderate candidate with no agenda No voting public prefers other candidates, and moderate candidate as backup. I give you an example I posted in another thread: * 60% want a dem candidate to win * 40% want a rep candidate to win * 70% are willing to join strategic voting to avoid allowing other party to win In this case, the dem candidate looks like a correct winner. With ranked choice the the dem candidate would win. But with approval voting strategic "moderate" candidate wins. If they are moderate, that's good. But they can easily be just weak nobody. It is not exactly what voting public prefers. That choice is a fake choice, like a girl, do you want to go to bed or be thrown into a forest with angry wolves. > if there's no particularly compelling reason for people to want that person to be president. The reason is to not let opposing party win. Strategic voting. > If both major parties (assuming there are two, maybe there'll be more...) nominate not-so-great candidates, then the voters have an option to elect someone like Tom Hanks. And they will if it is some form of ranked choice, but not just approval.

Why is Instant Runoff Voting the worst possible voting method?

by _AzMoo 5y ago

Why is Instant Runoff Voting the worst possible voting method?

"Worst possible" might be a bit strong, but an important property that a voting system should have is that it finds the Condorcet winner if one exists. The Condorcet winner is the candidate who beats every other candidate in a head-to-head election. IRV is not guaranteed to find a Condorcet winner. The problem with IRV is that you can have a candidate who is everyone's second choice, but then loses out on the first ballot because too few people ranked them first.

slownews45 5y ago
I've been voting RCV and I've yet to see this actually occur in practice. The candidates who are marketing themselves so well that they are second on almost everyone's ballot (in a 13 person race!) are generally FIRST on a fair number (relative to all 13 folks).
- obelos 5y ago
  This is what happened in Burlington, VT that prompted them to repeal IRV/RCV: https://electionscience.org/library/irv-and-core-support/ https://electionscience.org/library/irv-and-core-support/
  - slownews45 5y ago
    Fantastic. Thanks for link. Would screening for a condorcet winner (beats all winner) FIRST then proceeding to RCV address this concern sufficiently? Ballot completion would remain unchanged.

throw_away 5y ago

Worst possible ranked choice alternative, not worst possible voting method (i.e., still better than FPTP, but not without its weaknesses). Frustrating as there are more straightforward, and objectively better mechanisms which are ignored in favor of IRV. It's hard not to feel conspiratorial that maybe the Powers That Be want worse voting mechanisms. This page is a good explainer of IRV's weaknesses and shows some of the alternatives: https://ncase.me/ballot/ https://ncase.me/ballot/

dane-pgp 5y ago
> not worst possible voting method Since you mention it, let me offer a candidate for "worst possible voting method (that has actually been used in a democracy)", namely "plurality-At-Large".[0] It basically takes the worst properties of FPTP and extends them to an entire governing body, allowing a party with less than 50% support to win 100% of the seats (by design). Fortunately it has been mostly abandoned in the US thanks to the Voting Rights Act and subsequent SCOTUS decisions. [0] https://www.nonprofitvote.org/the-bias-of-at-large-elections-how-it-works/ https://www.nonprofitvote.org/the-bias-of-at-large-elections...
- dragonwriter 5y ago
  > Fortunately it has been mostly abandoned in the US thanks to the Voting Rights Act and subsequent SCOTUS decisions. A close variant (vote for up to N, top N win, at large) is used in a lot of local elections still; all multimember district methods are banned in House elections specifically to prevent plurality at large from being used there. (Though the Senate uses temporally-segregated two-seat plurality at large in every state.)
  - dragonwriter 5y ago
    > (Though the Senate uses temporally-segregated two-seat plurality at large in every state.) Correction: it uses either that or similarly segregated majority/runoff, varying by state. Majority/runoff and plurality are similar FPTP variants, but majority/runoff is slightly less bad.

dragonwriter 5y ago

A succinct version (others have linked more detailed, largely outcome-oriented analyses, which are also valid and important) is that, of seriously-considered ranked-ballots methods, it both throws out the most information from the ballots and uses information rather unequally across ballots, attempting to simulate FPTP elections with narrower candidate pools until you get a majority winner.

elihu 5y ago

One of it's big downsides is that you can, in some cases, cause a candidate to lose by ranking them too highly. In voting-theory terminology, it fails the monotonicity criterion. In at least that one respect it's worse than first-past-the-post. (I mean, imagine if people could say "Gore would have won in 2000 if only a few less people had voted for him". That sounds nonsensical, but that's how IRV works sometimes.) Wikipedia has an example: https://en.wikipedia.org/wiki/Monotonicity_criterion#Instant-runoff_voting_and_the_two-round_system_are_not_monotonic https://en.wikipedia.org/wiki/Monotonicity_criterion#Instant... I think first-past-the-post and IRV are both bad voting systems that are unsuitable for real-world use in elections with more than 2 candidates. Approval voting is simpler than IRV and (as far as I know) it isn't worse than FPTP in any way, so I think we should push for that.

asteroidbelt 5y ago
> Approval voting is simpler than IRV and (as far as I know) it isn't worse than FPTP in any way FPTP might be better than approval voting, because approval voting favors weak moderate candidates with no agenda. With FPTP the people alternate lefts and rights and the system develops. With moderate candidates the system may stop progressing: no reforms, no bugfixes.
- elihu 5y ago
  If the voting public prefers a weak moderate candidate with no agenda, then that's the candidate that should win. I think weak moderates usually flop, though, if there's no particularly compelling reason for people to want that person to be president. The way I look at is that it's a kind of relief valve. If both major parties (assuming there are two, maybe there'll be more...) nominate not-so-great candidates, then the voters have an option to elect someone like Tom Hanks. I mean, I would have voted for Tom Hank in 2016 if I had an approval voting ballot and he was one of the options.
  - asteroidbelt 5y ago
    > If the voting public prefers a weak moderate candidate with no agenda No voting public prefers other candidates, and moderate candidate as backup. I give you an example I posted in another thread: * 60% want a dem candidate to win * 40% want a rep candidate to win * 70% are willing to join strategic voting to avoid allowing other party to win In this case, the dem candidate looks like a correct winner. With ranked choice the the dem candidate would win. But with approval voting strategic "moderate" candidate wins. If they are moderate, that's good. But they can easily be just weak nobody. It is not exactly what voting public prefers. That choice is a fake choice, like a girl, do you want to go to bed or be thrown into a forest with angry wolves. > if there's no particularly compelling reason for people to want that person to be president. The reason is to not let opposing party win. Strategic voting. > If both major parties (assuming there are two, maybe there'll be more...) nominate not-so-great candidates, then the voters have an option to elect someone like Tom Hanks. And they will if it is some form of ranked choice, but not just approval.