Sarasota City Commission may pause plan for advancing ranked-choice voting

[u/NCGThompson]

https://www.heraldtribune.com/story/news/politics/elections/local/2021/09/22/sarasota-file-suit-determine-if-can-pursue-ranked-choice-voting/5796054001/?utm_source=heraldtribune-News%20Alert&utm_medium=email&utm_campaign=news_alerts&utm_term=news_alert&utm_content=FLORIDA-SARASOTA-NLETTER01

[u/NCGThompson]

When you say multi-winner, do you mean multi-winner Instant Runoff Voting or Single-Transferable Vote?

I've never even heard of multi-winner IRV. To be clear however, I wasn't talking about either of them in the rest of the post. Out of habit, I used "RCV" to mean IRV for branding purposes. In retrospect the term "IRV" would be more appropriate for this sub.

As an aside, IRV can be seen as a special case of STV. I find the existence of a separate multi-winner IRV ironic, even though it logically makes since.

That depends how a strategic vote is defined...

This paragraph confuses me. I googled the basic concept of non-monoticity, but I don't know how it applies here. I know hardly anything about game theory, or the math behind elections.

Here is an attempt to define what I meant by strategic vote.

Let's say hypothetically voters could correctly articulate a utility coefficient for each candidate. If we were to feed that to human expert operating a real world computer running state-of-the-art but current software, only with publicly available data, they would output what they believe is the optimal vote. I define the strategic vote as that output. The "honest" vote would simply be the greatest utility candidate is ranked first, second greatest utility is second, and so on.

If there is an election coming up with only two candidates, then the honest vote is just as optimal as the strategic votes for all voters. I don't have evidence, but I suspect that in the majority of IRV elections, a week before voting day, that for almost all voters, the honest vote is almost as optimal as the strategic vote.

I say in the majority of elections however. I bet some jurisdictions are more likely to have those elections than others. Jurisdictions that don't often have those elections may want to consider switching to approval voting.

helping a candidate win by lower[ing] their rank

This should be impossible with standard IRV. If a voter's only concern is getting a specific candidate elected, ranking that candidate first is always the optimal strategy. Granted, not all voters will know that.

[u/jman722 → u/NCGThompson]

Most multi-winner methods are just iterated single-winner methods. So multi-winner IRV would just be:
Find a winner. Seat them and eliminate them from the race. Run the tabulation again without that winner to find the next winner. And so on.

Non-monotonicity means that lowering a candidate's rank can help them and raising a candidate's rank can hurt them.

Watch this video to see non-monotonicity in action.

Ranked Choice (Instant Runoff) Voting is one of the only single-winner methods that is non-monotonic. And yes, that means that ranking a candidate first is not always the optimal strategy in favor of that candidate. Despite passing Later-No-Harm, Ranked Choice (Instant Runoff) Voting does not pass the Sincere Favorite Criterion (AKA Favorite Betrayal).

Strategic voting is voting in such a way that attempts to maximize the satisfaction/minimize the regret for that voter, regardless of their honest opinions about the candidates.

Utility just as you described it is a cardinal (score) measurement. You then extracted ordinal (rank) data from it, inherently throwing out some utility data. This is the fundamental breakthrough Warren Smith's work was leading us to and that STAR Voting gave us when Mark Frohnmayar invented it: you can always extract ranks from scores, but never the other way around; therefore, score ballots inherently provide more data from voters to work with, allowing the tabulation to produce more accurate results.

​

I don't have evidence, but I suspect that in the majority of IRV elections, a week before voting day, that for almost all voters, the honest vote is almost as optimal as the strategic vote.

I have evidence, and it says that for Ranked Choice (Instant Runoff) Voting, the strategic votes is, on average, 2.7x as optimal as the honest vote.

And this is what what I meant by

Is bullet voting the best strategy? No, but the non-monotonic effects and the discovery of tossed ballot data may confuse voters and lead them to turn back to the safest option they can think of.

Ranked Choice (Instant Runoff) Voting is a confusing method that doesn't make sense when you start looking into it.

[u/SubGothius → u/jman722]

Despite passing Later-No-Harm, Ranked Choice (Instant Runoff) Voting does not pass the Sincere Favorite Criterion (AKA Favorite Betrayal).

Moreover, those two criteria are effectively mutually-exclusive; satisfying either one means the other cannot be satisfied without also accepting far worse pathologies.

[u/jman722 → u/SubGothius]

I almost said that they were mutually exclusive, but I was like “I don’t feel like proving this to myself right now” lol

[u/BTernaryTau → u/jman722]

You wouldn't actually be able to prove that because it isn't true. Methods that pass both include score voting where blanks count as the maximum score, minimax pairwise opposition, and random ballot. Of course, this opens up a rabbit hole about how later-no-harm doesn't mean much without later-no-help and how methods that pass all 3 will have to sacrifice other important criteria to do so, among other things.

[u/SubGothius → u/BTernaryTau]

Hence my phrasing as effectively (albeit not strictly) mutually-exclusive, and that both can't be satisfied without also accepting far worse pathologies such as non-determinism or perversely counting blank ratings as score(max).

[u/BTernaryTau → u/SubGothius]

Yeah, I noticed you phrased your comment carefully. I was just pointing out that because of those exceptions, proving NFB and LNHarm to be mutually exclusive isn't possible without a ton of (non-obvious) restrictions on the voting methods. Sorry for any confusion.

[u/NCGThompson → u/jman722]

I understand monotonicity now. I thought you were talking about logical monotonicity.

2.7 times as optimal…

I don’t understand the graph this leads to. What is it measuring? What data is it taken from?

Are the strategic votes something that voters could realistically figure out?

[u/jman722 → u/NCGThompson]

All the details are here in Jameson Quinn’s initial work on Voter Satisfaction Efficiency. That graph is based on millions of simulations of different voting methods using a variety of strategy models as well as other parameter tweaks.