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RCV encompasses a lot of different systems, but the most common instantiation is something resembling instant runoff, and I am skeptical that it drives towards

RCV encompasses a lot of different systems, but the most common instantiation is something resembling instant runoff, and I am skeptical that it drives towards the middle. If we believe that the appropriate compromise is no one's first choice, the first thing IRV does is throw away any "appropriate compromise".

ChadNauseam 4y ago
Yep. Actually the behavior of IRV is extremely unintuitive (despite how nice it sounds). Even using very simple models that assume every voter has political opinions completely described by a 2d political compass, prefers candidates that are closer to them on the compass, and that voters are normally distributed around a central point, you get very strange behavior! Here are some diagrams that illustrate the effect: https://rangevoting.org/IEVS/Pictures.html https://rangevoting.org/IEVS/Pictures.html interestingly, IRV is not even monotonic! It's easy to construct a situation where converting people to have the same ranking as you causes you to get a candidate you like less. (The concave parts of the voronoi diagrams describe areas where this happens.) If you're curious about this, a few years back some friends and I tried to make a video describing this phenomenon: [0]. (Our editing and presentation skills are nothing to write home about but I think the video is interesting.) [0]: https://www.youtube.com/watch?v=0m7vtt9jXpM https://www.youtube.com/watch?v=0m7vtt9jXpM
- throw_away 4y ago
  Here is another, interactive explanation of this phenomenon in IRV, as well as some alternatives that do not suffer this issue: https://ncase.me/ballot/ https://ncase.me/ballot/
- panick21_ 4y ago
  I don't understand why Ranked is so popular. Range voting is just easier and better in every single way.
  - dllthomas 4y ago
    > better in every single way. Range can't satisfy Condorcet (that is, if there is a candidate that would win every head-to-head, that candidate should win the election). Of course, the most common approaches to RCV also fail that criterion, but it's potentially a way some ranked methods are better than range methods.
    - panick21_ 4y ago
      > Range can't satisfy Condorcet That is not necessary a desirable feature. If that is desirable or not depends on your value system of what elections should achieve. What is 'fair' or 'correct' is not universal.
      - dllthomas 4y ago
        Granted, but it seems a reasonable enough thing to ask for that "better in every single way" deserves qualification.
abirch 4y ago
Most US districts are not competitive. E.g., there's an almost zero chance that AOC, MTG, Cawthorne, etc. loses in the general election. You have a higher probability of losing a primary than a general. If a moderate of their party runs, it'd be easy for their own members to vote for the moderate as #1 ahead then #2 the more extreme person, and not for the awful evil other party person. The opposition can also vote for the moderate of the dominant party, #1, their candidate #2, and not for the aweful extremist.
- dllthomas 4y ago
  I think that's true, and pushes things more extreme, but is pushed against (incompletely) by jungle primaries and to a lesser extent by open primaries; and ... I don't see the relationship with RCV, which was all I was discussing. Did you mean to respond one level up?
  - deleted 4y ago
    [deleted]
  - abirch 4y ago
    I'm not disagreeing with you about the instant runoffs for competitive elections. Then the more moderate could get squeezed out. The relationship with RCV for non-competitive races (e.g., those districts that are gerrymandered or naturally not competitive which is the majority in the USA) is the RCV can easily address the extremes versus moderates. Moderate candidates don't run because they won't get support from their party and are perceived to be stealing votes. E.g., If you're not voting for $EXTREMIST you're voting for the $THEM. RCV lets you vote for the moderate AND your party's extremist in order to thwart the other side.
lkrubner 4y ago
"If we believe that the appropriate compromise is no one's first choice" The winner in RCV will always be someone's first choice.
- dllthomas 4y ago
  No, some methods of counting rank choice ballots will sometimes pick a candidate who was no one's first choice. In particular, this must be so for any Condorcet method, because the Condorcet winner might be no one's first choice (imagine a setting where 1/3 of voters want candidate A then D, 1/3 want B then D, and 1/3 want C then D; 2/3 of voters would vote for D whether run head-to-head against A, B, or C, and yet D got no first place votes). In instant runoff it is certainly true that the winner is always someone's first choice, and that was my point - sometimes the winner the method selects should not be the winner.

ChadNauseam 4y ago

Yep. Actually the behavior of IRV is extremely unintuitive (despite how nice it sounds). Even using very simple models that assume every voter has political opinions completely described by a 2d political compass, prefers candidates that are closer to them on the compass, and that voters are normally distributed around a central point, you get very strange behavior! Here are some diagrams that illustrate the effect: https://rangevoting.org/IEVS/Pictures.html https://rangevoting.org/IEVS/Pictures.html interestingly, IRV is not even monotonic! It's easy to construct a situation where converting people to have the same ranking as you causes you to get a candidate you like less. (The concave parts of the voronoi diagrams describe areas where this happens.) If you're curious about this, a few years back some friends and I tried to make a video describing this phenomenon: [0]. (Our editing and presentation skills are nothing to write home about but I think the video is interesting.) [0]: https://www.youtube.com/watch?v=0m7vtt9jXpM https://www.youtube.com/watch?v=0m7vtt9jXpM

throw_away 4y ago
Here is another, interactive explanation of this phenomenon in IRV, as well as some alternatives that do not suffer this issue: https://ncase.me/ballot/ https://ncase.me/ballot/
panick21_ 4y ago
I don't understand why Ranked is so popular. Range voting is just easier and better in every single way.
- dllthomas 4y ago
  > better in every single way. Range can't satisfy Condorcet (that is, if there is a candidate that would win every head-to-head, that candidate should win the election). Of course, the most common approaches to RCV also fail that criterion, but it's potentially a way some ranked methods are better than range methods.
  - panick21_ 4y ago
    > Range can't satisfy Condorcet That is not necessary a desirable feature. If that is desirable or not depends on your value system of what elections should achieve. What is 'fair' or 'correct' is not universal.
    - dllthomas 4y ago
      Granted, but it seems a reasonable enough thing to ask for that "better in every single way" deserves qualification.

abirch 4y ago

Most US districts are not competitive. E.g., there's an almost zero chance that AOC, MTG, Cawthorne, etc. loses in the general election. You have a higher probability of losing a primary than a general. If a moderate of their party runs, it'd be easy for their own members to vote for the moderate as #1 ahead then #2 the more extreme person, and not for the awful evil other party person. The opposition can also vote for the moderate of the dominant party, #1, their candidate #2, and not for the aweful extremist.

dllthomas 4y ago
I think that's true, and pushes things more extreme, but is pushed against (incompletely) by jungle primaries and to a lesser extent by open primaries; and ... I don't see the relationship with RCV, which was all I was discussing. Did you mean to respond one level up?
- deleted 4y ago
  [deleted]
- abirch 4y ago
  I'm not disagreeing with you about the instant runoffs for competitive elections. Then the more moderate could get squeezed out. The relationship with RCV for non-competitive races (e.g., those districts that are gerrymandered or naturally not competitive which is the majority in the USA) is the RCV can easily address the extremes versus moderates. Moderate candidates don't run because they won't get support from their party and are perceived to be stealing votes. E.g., If you're not voting for $EXTREMIST you're voting for the $THEM. RCV lets you vote for the moderate AND your party's extremist in order to thwart the other side.

lkrubner 4y ago

"If we believe that the appropriate compromise is no one's first choice" The winner in RCV will always be someone's first choice.

dllthomas 4y ago
No, some methods of counting rank choice ballots will sometimes pick a candidate who was no one's first choice. In particular, this must be so for any Condorcet method, because the Condorcet winner might be no one's first choice (imagine a setting where 1/3 of voters want candidate A then D, 1/3 want B then D, and 1/3 want C then D; 2/3 of voters would vote for D whether run head-to-head against A, B, or C, and yet D got no first place votes). In instant runoff it is certainly true that the winner is always someone's first choice, and that was my point - sometimes the winner the method selects should not be the winner.