Comment by Tiktaalik
10 hours ago
No electoral method is perfect and there are problems with Instant runoff ranked ballots. Look up "Favourite Betrayal" as a problem where ranking your most favourite incorrectly can accidentally result in your least favourite winning.
Of course just because there are technically flaws, doesn't mean it's not an improvement over the status quo.
Instant Runoff Ranked ballots are particularly well suited for electing a single position like a Mayor or President. Given that it's still a majoritarian system like First Pass the Post, it's a much more questionable system to use for other things like electing a parliament.
I think IRV at least has fairly unpredictable failure cases, which means they can't be exploited.
I remember seeing a 2D chart representing voter preferences on the X and Y axis, coloured by who wins under those preferences (and some symmetry-breaking assumptions). Some systems showed clear biases towards certain outcomes. IRV had a pretty symmetric shape but with a splotch in the middle that was a random jumble of different colours - an unpredictable, chaotic outcome.
Might have been these charts: https://www.rangevoting.org/IEVS/Pictures.html
> Of course just because there are technically flaws, doesn't mean it's not an improvement over the status quo.
The problem IMO is when there's better options but it's hard to get people to care enough to switch systems again. I'm hoping Ranked Robin can catch on so at least places that went to IRV can switch to a better system without new ballots.
In Star Vote Favourite Betrayal still exists, but its very rare.
The issue is that you can't have 'Later No Harm' and 'Favorite Betrayal' at the same time.
Star Vote scores high on both but it can't be perfect.
See: https://link.springer.com/epdf/10.1007/s10602-022-09389-3?sh...
PS for those that don't know:
STAR Voting (Score Then Automatic Runoff) works in two stages: 1. Voters score candidates from 0 to 5. 2. The two candidates with the highest total scores become finalists. 3. The finalist preferred by more voters wins.
So it combines score voting and runoff. Meaning it favors centrist candidates that are prefered by most people over somebody that can turn out the base.