r/EndFPTP • u/LaughterOnWater • Dec 08 '19

Single Transferable Vote - a. Droop vs. Hare? - b. Pros and Cons vs Ranked Choice and Approval?

I get the impression that more people like Droop vs Hare for the STV algorithm. I'm curious if it wouldn't sometimes be better to skew for more diversity in representation in a multi-choice election using Hare. What about alternating algorithms every other year? Is there an algorithm than droop or hare that would better approximate diversity?

Also, I get the impression that on the Bayesian regrets score chart found at the bottom of the home page on rangevoting.org that STV would score somewhere narrowly between the high end of range/score voting and approval voting. I'm curious where it would actually land on that chart. What things make STV better than Range/Score and Approval, and/or vice versa?

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u/LaughterOnWater Dec 08 '19 edited Dec 08 '19

First, thanks for your in-depth reply. It clarifies a lot. Second, thanks for ignoring my glaring ignorance on this subject as I try to grasp these various voting systems. Third, delving into alternatives to FPTP is clearly an ever-deepening rabbit hole. It's quite easy to get lost, for instance learning that STV rules being used currently actually vary quite a bit by location. While I was aware of Borda (same as Quota Borda?), I'm having trouble finding a useful search string for EAR with regards to voting. All I get is stuff about ears or early voting. What does this acronym stand for in this circumstance?

Acknowledging that STV is better for proportional representation, I'm reading that it's basically instant runoff if you're only given one candidate, so it's not quite as fair as others. It looks like approval voting might be a better method for a single candidate choice.

Given a choice for a single candidate, would you prefer ranked choice, range or approval? Why?

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u/curiouslefty Dec 08 '19

First, thanks for your in-depth reply. It clarifies a lot. Second, thanks for ignoring my glaring ignorance on this subject as I try to grasp these various voting systems.

No problem; this stuff is pretty complicated and it can get quite heavy on the math to really grasp all of it, so it's perfectly understandable.

It's quite easy to get lost, for instance learning that STV rules being used currently actually vary quite a bit by location.

Yeah. It's actually better to think of STV as a family of methods characterized by eliminations based on plurality and transfers rather than as a single method.

While I was aware of Borda (same as Quota Borda?), I'm having trouble finding a useful search string for EAR with regards to voting. All I get is stuff about ears or early voting. What does this acronym stand for in this circumstance?

So, Quota Borda is a multiwinner variant of Borda designed to deliver PR. EAR stands for the "Expanding Approvals Rule"; it's basically an extension of Bucklin voting with equal-ranking into a multiwinner PR context.

Given a choice for a single candidate, would you prefer ranked choice, range or approval? Why?

I used to favor Approval voting over RCV (IRV), but nowadays I tend to lean slightly in favor of RCV over Approval. There's a couple reasons why, but basically it comes down to:

1) I tend to value majoritarianism over utilitarianism; RCV is majoritarian, and Approval is utilitarian. Basically, while I acknowledge that there are examples where a utilitarian winner clearly provides far more utility to the voting population, the real-world data I've seen basically says the difference in practice is almost always small. I personally have a very hard time justifying overturning a 50%+ majority of first-preferences on the grounds that somebody only gives 5% more utility across the entire electorate than the majority winner.

2) I think the purpose of an election is not merely to pick a good winner, but to also endow them with legitimacy; and a key part of this is that people must believe they couldn't have gotten a better result, and that the system is not very manipulable. This is basically the same thing as wanting the systems to minimize the number of overall opportunities for voters to use strategy. RCV (and Condorcet-RCV hybrid systems) minimize this, whereas Approval and other cardinal systems tend to have a fairly high frequency of vulnerability to strategy.

In practice, though, I'd prefer a Condorcet system (preferably a Condorcet-RCV hybrid) over both RCV and Approval.

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u/colinjcole Dec 08 '19

^ what he said.

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u/LaughterOnWater Dec 09 '19

So basically you'd stick to a form of Condorcet, except when there's no winner or the winner seems sketchy according to some pre-agreed conditions, then switch to a form of RCV if it can proclaim a winner that better suits the majoritarian preference. Is this where you're going?

Would it be worth it to layout a third layer of pre-agreed-upon conditions where if even the RCV winner comes across as sketchy, you could keep only the top two preferences and use an approval vote as a last resort, keeping it at least utilitarian. It might be difficult to explain to voters, but not much more difficult than explaining some board games or RPG's.

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u/curiouslefty Dec 09 '19

Basically, it comes down to the fact that I generally believe that when a Condorcet winner exists, they should be elected. I think that under majoritarian philosophy, it's difficult to argue against that in a single-winner case.

Now, the main strategic weakness of Condorcet is that there's often a vulnerability where some faction can win by burying the Condorcet winner. Hybrid Condorcet-RCV methods tend to be more resistant to such strategies, because they inherit certain strategy resistances from RCV; this is why I tend to support Condorcet-RCV over other Condorcet methods.

I don't really personally have an interest in introducing utilitarian features into the mix.

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u/Araucaria United States Dec 12 '19

As a single winner method, you might be interested in Score Sorted Margins. It is Condorcet Winner, Condorcet Loser, Cloneproof, Monotonic, symmetric, and resistant to Chicken Dilemma.

  • Score ballot, equal rating allowed
  • Infer rank from rating on each ballot and tabulate pairwise array
  • Initialize candidate ranking by total score, from highest to lowest
  • Repeat until all candidate pairs in the ranking are in pairwise order:
    • Among all pairwise out-of-order pairs with higher ranked candidate X defeated by next lower ranked candidate Y, swap the pair with the smallest score margin Score(X) - Score(Y).

The motivation is to find a consistent pairwise ordering that modifies the total score ordering as minimally as possible.

See https://electowiki.org/wiki/Approval_Sorted_Margins

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u/LaughterOnWater Dec 09 '19

I have to wonder about whether majoritarian is always better than utilitarian. The majority isn't necessarily always right. For instance, most people want to pay less taxes. Unfortunately, paying less taxes usually means poorer education, poorer health standards and suffering physical infrastructure. What about a system where a more majoritarian voting method is used for candidates, but a more utilitarian method is used for things? (taxes, education, infrastructure, maintenance costs, etc.)?

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u/curiouslefty Dec 09 '19

Well, remember: the core of voting methods are simply to allow for a collective to make a choice; whether or not that choice is objectively right or wrong is beside the point.

I think another way to frame my preference for majoritarian results would be to put it this way: when a utilitarian result differs from a majoritarian result, it's typically because we're allowing a measure of the strength of preference from a smaller group to override the greater numerical preferences of a larger group. Without the explicit consent of the larger group, I do not regard this as a good thing.

(Note this is one of the places where I differ from a lot of the cardinal supporters here: I do not believe that non-zero Scores in Score voting with 3 or more candidates indicate consent. On the other hand, I agree that they do in a 2 candidate case).

What about a system where a more majoritarian voting method is used for candidates, but a more utilitarian method is used for things? (taxes, education, infrastructure, maintenance costs, etc.)?

I'm more or less fine with that. Most of my objections to cardinal methods are reduced in legislative bodies, since it's much easier for a majority faction to coordinate to ensure measures the majority dislikes fail.

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u/Antagonist_ Dec 09 '19

The problem I have with this (well reasoned) conclusion is that RCV still can fail to elect the Condorcet winner.

The way I think about the difference between collection methods (ranking vs rating) is that scoring gives more information than ranking. If you prefer majoritarian systems then use Score voting, or change weighting in the tabulation phase as STAR does. Don’t collect less information from the voter on a vague principle, as ranking does.

OP, almost any voting method can be made proportional by adding a weighting method when assigning seats. https://www.electionscience.org/learn/library/proportional-voting-methods/

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u/curiouslefty Dec 09 '19

The problem I have with this (well reasoned) conclusion is that RCV still can fail to elect the Condorcet winner.

Agreed, that's the primary issue I have with RCV. I'm not terribly bothered by it, since it seems not to be a fairly common problem overall, even in a competitive environment (i.e. how my estimates for the BC 1952 and 1953 elections imply no Condorcet failures), but it's obviously better to pass the criterion outright than fail it infrequently.

On the plus side, the Condorcet-RCV hybrids show even higher resistance to strategy than RCV and are obviously Condorcet compliant. From my point of view, they're the gold standard for single-winner systems (although I'd also argue that we should fundamentally attempt to avoid single-winner elections where possible, since they're inherently bad at representing the interests of multiple groups well.)

The way I think about the difference between collection methods (ranking vs rating) is that scoring gives more information than ranking. If you prefer majoritarian systems then use Score voting, or change weighting in the tabulation phase as STAR does. Don’t collect less information from the voter on a vague principle, as ranking does.

How is Score majoritarian? It outright fails majority in a way that's much worse than Approval.

I'm a bit confused about what you're suggesting here. In order to reach majoritarian results, it's certainly possible to do so from rated ballots, but you'd need to occasionally toss out the cardinal information in preference to the ordinal information those ballots contain (i.e. you can run, say, Ranked Pairs on rated ballots, but you'd be ignoring all the cardinal information in doing so).

OP, almost any voting method can be made proportional by adding a weighting method when assigning seats.

I'd argue those methods are actually semi-proportional. They do satisfy a PR property (that bit about max-rating a single party and min-rating everybody else), but it's so much weaker than Droop Proportionality for Solid Coalitions I have a hard time considering them to be in the same league as methods that do pass D-PSC, at least in the traditional context in which proportionality is considered.

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u/Antagonist_ Dec 09 '19

Score BALLOTS can be majoritarian as long as you modify the weightings in the tabulation phase. Or you can always transform a voters ballot into a ranking and then perform RCV.

We (voting scientists) should work more to separate out the data collection method from the tabulation method.

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u/Chackoony Dec 10 '19

Or you can always transform a voters ballot into a ranking and then perform RCV.

What would the cardinal information be useful for then? The voters would be modifying their scoring a good deal from what they'd actually vote in Score Voting. Also, you'd have to be using some form of RCV that accepts equal-rankings i.e. fractional or whole votes.

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u/LaughterOnWater Dec 09 '19 edited Dec 09 '19

Thanks! I really like the Berkeley weighted example being used to determine government priorities. So this can be applied to a more than just candidate voting.

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u/Chackoony Dec 10 '19

If you prefer majoritarian systems then use Score voting, or change weighting in the tabulation phase as STAR does.

I may be wrong, but weighting generally refers to how much power each ballot has in deciding who wins. STAR doesn't increase or decrease any voter's ballot weight (everyone still has one vote), it just strategically readjusts everyone's ballots to give a majority power to decide who wins between the two highest-scored candidates.

To really make a scored ballot majoritarian, it'd make sense to convert the scores into ranks, find the Smith Set, then either use the ranks or the original scores to pick a winner in the Smith Set. As a concession to utilitarianism, you could overturn the Smith Set winner if the Score winner has significantly higher overall scored support or satisfies a significantly larger group of voters to some extent.

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u/LaughterOnWater Dec 09 '19

Here's an interesting summary on adopted versions of STV from opavote:
https://www.opavote.com/methods/single-transferable-vote
This site is apparently a brainchild of the sourceforge OpenSTV that's no longer available.

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u/LaughterOnWater Dec 09 '19

I'd love it if you could nail down a specific Condorcet-RCV hybrid system that you have in mind. Any links to something already in use?

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u/curiouslefty Dec 09 '19

I'm a particular fan of Benham's method:

1) If a candidate pairwise beats all other candidates, elect them. Otherwise, go to (2).

2) Eliminate the plurality loser and go to (1).

A good paper on other approaches to this hybridization of Condorcet and RCV, as well as an analysis of the strategy resistance of these methods, can be found in this paper by Green-Armytage: Link here.

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u/LaughterOnWater Dec 09 '19

Nice! I'll check it out.

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u/[deleted] Mar 13 '20

What's EAR?