I think you missed the part where I said that it can happen, but that it’s rare and hard to predict.
Yea, sorry, my wording wasn’t the clearest. I meant to say that it is actually not that rare, and hoped that the linked source would help support that claim. From the same website:
We can [assume that] “all votes [are] equally likely except that the probabilities that A,B,C will be middle-ranked of the three in that vote are 30%, 30%, and 40% respectively” where C is the 3rd-party candidate. Then in IRV as #voters→∞, C’s probability of winning is probably exponentially tiny so that Joe Voter is justified in assuming C only a very tiny […] chance of winning. Indeed C only has a tiny chance of merely surviving the first round. However, Joe reasons, if Joe and friends by honestly-ranking C top do manage to make C survive the first round, then that will almost certainly happen only at the cost of eliminating Joe’s second-favorite candidate A. If the A votes then transfer equally to C and B (which in “1-dimensional politics” with C A B arranged along a “line” in that order, seems likely) then C will almost certainly still lose, and will have deprived A of victory in the process.
The idea then would be that the behavior of mid-ranking the 3rd party candidate would be self-reinforcing in IRV: an assumption of a slight bias that way like we just made (40% versus 30% […]), then leads to it being strategically wise for Joe Voter to do it, leading to a larger bias that way, etc. – positive feedback, self-reinforcing 2-party domination.
Approval Voting is bad because of the simple fact that it doesn’t let you express any preference.
I agree and that’s why I support Score Voting over it! The mechanism to express that one candidate is better than another one is to just give them honest scores! And there’s studies proving that’s the reality is, the vast majority of people are at least somewhat honest when filling out a Score ballot
Zagorath@aussie.zone 2 days ago
Cardinal systems devolve into approval, and approval doesn’t allow expressing preference. And being unable to express preference lends itself to some of the worst strategic voting and reintroduces the spoiler effect in the place it’s most important to avoid the spoiler effect: serious 3-(or more-)way races. If I’m an A voter, B is centrist, and C is worst, then under approval it’s fine for me to approve of A and B if I know A can’t win. But the moment A is a serious contender, choosing to approve of B decreases the chance A might win. But not approving of B increases the chance C might win. I’m stuck with having to make a terrible decision.
Ordinal systems don’t do this. Some ordinal systems might be better than IRV and avoid the biggest criticisms of that system, but ordinal systems beat cardinal systems nearly every time.
But the main thing about all of this is that every single-winner system is always worse than proportional multi-winner systems. Moving to any system other than FPTP should be the first priority, but if you’re going to spend time knocking down suggestions to improve to the most well-proven alternative, you might as well go all the way and advocate MMP or direct proportional, and on shoring up some of the weaknesses of that system (such as problems with party lists letting parties choose who gets in even if people don’t like the candidate of the party they like, or how minimum thresholds can lead to some people’s votes being effectively wasted).