Posts made by Isocratia

Does anyone know if BTR-Score is immune to turkey-raising / DH3?

I saw a post on here which said that German courts have ruled that nonmonotonic voting methods are unconstitutional.

Does anyone have more info about this?

I've coined the term "lazy fingers assumption" to refer to a principle that can be used to analyze tactical bullet voting under voting methods that satisfy the later no harm criterion. The idea is that if a voter knows that adding a ranking has literally 0% chance of altering the election (i.e. the voting method won't even look at that information) then they will not add that ranking.

Under the lazy fingers assumption, in IRV, any voter whose favorite candidate is one of the 2 finalists (and the finalists were foreseeable) will bullet-vote.

The opposite assumption is the "expressive voter assumption", which assumes that voters will add rankings despite knowing that it has a 0% chance of affecting the election.

Approval voting constantly gets attacked by Fairvote people who outright lie about it.

@chocopi

It's not exactly true of plurality voting. In plurality, there can be multiple Myerson-Weber equilibria (fixed points where the voters vote tactically based on beliefs about the likely winners that are later matched by the actual result). The Condorcet winner wins in some but not all.
To use a contrived example:
~50% of voters: A > B > C
~50% of voters: A > C > B

If the voters believe that A is one of the two likely frontrunners, then A will win with 100% of the vote. That is one Myerson-Weber equilibrium.

But if the voters believe that B and C are the likely frontrunners, then A will lose with 0% of the vote. That is the other Myerson-Weber equilibrium. And even though they would all be better off if they all voted for A, any individual voter unilaterally switching their vote to A will only make the outcome worse from their own perspective.

Approval voting eliminates this kind of absurd equilibrium simply by allowing voters to vote for multiple candidates instead of "switching" their vote from one candidate to another. In the example above, if voters believe that B and C are the frontrunners, then they all approve A anyway, and A wins with 100% approval. So the second, suboptimal equilibrium is eliminated.

Isn't the chicken dilemma kind of a myth? It contradicts the theorem that approval and score voting elect the Condorcet winner under 100% tactical voting.

@cfrank

I have no kind words about quadratic voting. It has no apparent rationale for the way it's designed, and it has very high front-end complexity which is an absolute dealbreaker. Voters should not have to do math in the voting booth. It has the hallmarks of something invented by grifters to bamboozle people who don't know any better, like NFTs.

@cfrank

That could end up removing candidates that many voters regarded as unrepresentative of themselves but not antagonistic to them.

The idea is that voters would use AD votes for factions that are potential coalition partners for their faction. Some voters can be expected to overuse DD votes, which is why the first-phase disapproval threshold is high.

@cfrank The first phase would eliminate some candidates who might otherwise win in the second phase.

These would be candidates who've actively antagonized everybody outside their faction. In order for the first phase to matter, such a faction would have to be smaller than 1 - the first phase disapproval threshold, but large enough to win at least 1 seat proportionally.

Believe it or not, I was in an organization that was faced with such a scenario. They were using STV and the troll faction's candidate came in 1st because they all bullet-voted for him.

@cfrank That's what I said, the "phases" are part of the algorithm and voters only cast a ballot once.

I want to introduce a technique of combining two multiwinner approval methods using what I call vertical composition. The basic idea is that there are two "phases", both of which use approval ballots as their inputs, and the first phase filters out some candidates from entering the second phase. Voters, however, do not cast simple approval ballots, but ballots with trivalent values for each candidate - it is important to note that this is distinct from 0-1-2 score voting. The values are as follows:

• Approve in both phases (AA)
• Approve in first phase, disapprove in second phase (AD)
• Disapprove in both phases (DD)

The hypothetical fourth value, Disapprove in the first phase and Approve in the second phase, is excluded because it doesn't make sense.

My basic use-case for this technique is when the first phase is simple bloc approval voting that filters out anyone with more than, say, 75% disapproval (this threshold is a parameter), and the second phase is some proportional approval voting method.

This specific method would be useful for an organization that wants proportionality in its internal democracy but also wants to set up a barrier to prevent bad actors ("entryists") from joining the organization and winning a few seats proportionally while antagonizing everybody else in the organization. Voters would use DD votes to filter out the bad actors, and AD votes for candidates from different factions that are participating in good faith. A relatively high first-phase disapproval threshold, such as 75%, would make the method resistant to people overusing DD votes.

@masiarek

Condorcet method, so the main thing (in my view) to look out for is whether or not its cycle-resolving rule makes it immune to turkey-raising or not.
I've heard that a few Condorcet methods are immune to turkey-raising but I don't have more info about this.
Perhaps, in the event of a false Condorcet cycle generated by tactical voting, the smallest-margin victory will always belong to the "turkey".

@cfrank

It's in this paper from 2006
https://rangevoting.org/stratapproval4.pdf

@cfrank

Bullet voting is not the dominant strategy in score voting or approval voting for that matter. The dominant strategy is to identify the top 2 frontrunners, max-score the one you prefer, and min-score the other one. Then you max-score anyone else you like more than the frontrunner you just max scored. For some voters, that's a bullet vote, but not all.

If everyone uses this strategy, it elects the actual Condorcet winner. That's a theorem that's been independently discovered by several mathematicians.

@cfrank

I've heard that it's possible to make some Condorcet methods immune to turkey-raising by designing for a property called "dominant mutual third burial resistance." But I'm not familiar with examples of methods that do this, and it's been hard to find information about it. And in any case approval and score voting solve this problem in a much less complicated way.

@masiarek

I'm fairly sure it's straightforward. Look at the final two candidates, and any candidate ranked below either of them on a voter's ballot is red.

Edit: Also I think that example image is slightly wrong, the ballot that has D > F > B > ... should have B in black.

The main thing to watch out for in any modification of score voting is "does this create an incentive for turkey-raising." Turkey-raising is when a tactical voter raises bad candidates ("turkeys") above last place / zero score. It's extremely bad and it's infamous for ruining the Borda Count.

Score voting itself does not have turkey-raising (there's never a reason to give bad candidates anything other than 0). STAR doesn't have it either, because it's a combination of two methods that don't (score voting and some kind of automatic two-round system.)

This method looks like a combination of score voting and BTR. BTR has turkey-raising. There's an incentive to put turkeys ahead of a competitive rival in order to increase the rival's chance of being eliminated. So this method might have turkey-raising as well.

I believe that the later-no-harm criterion is so confusingly worded that people think it means something it doesn't. It's defined in terms of not harming a candidate, but people think that it means that adding a second, third, ranking etc. will never harm the voter. So they think that LNH means that every voter has an incentive to give their full ranking.

Because IRV fails the participation criterion, it's possible that the voter can be harmed even by adding their first choice. Sure, this will never change the winner from their first choice to someone else, but it could change the winner from their second choice to their 15th choice.

LNH is meaningless without the participation criterion and it's trivial to show that failing the participation criterion means that a voter can be harmed by adding their second choice as well (e.g. their first choice gets eliminated and their second choice causes a participation criterion failure).

The only method that satisfies both LNH and the participation criterion is... plurality voting. Or some kind of plurality-equivalent ranked voting which only looks at the first choices. And here it's clear that it only satisfies LNH by completely ignoring everything else after the first choice.

@wolftune
I noticed something similar with reweighted range voting when I tested it years ago. I had simulations with a "gray party" that got the same medium score from every voter, alongside colored parties that got the maximum score from their party voters and the minimum score from everybody else. I noticed that as I varied the score for the gray party, it would suddenly "explode" from having no seats to having all the seats.

I devised a fix, which I later learned was the Kotze-Pereira Transform.

For some reason I can only reply to posts in threads that I started. I can't post in threads that I didn't start. I want to post in the thread about "Allocated Score (STAR-PR) centrist clones."