[ethin]

This problem is only magnified when you consider our voting system. Any ranked voting system inherently runs into Arrow's Impossibility Theorem, which makes what we have right now not exactly democratic. The solution would be to switch to something like approval voting but good luck getting that going.

[mindslight]

It's been a while since I've studied the details of voting systems, but it seems like Approval voting just moves the spoiler effect into how people vote - ie strategic voting. Personally I think the possibilities of circular ties under Ranked Pairs is oversold.

Society is well acquainted with the concept of a tie, and whatever tiebreaker procedure we define probably won't factor into voter strategy all that much (that is, it will be less of an effect than the people who don't understand they can vote for more than one candidate)

[ClayShentrup]

> it seems like Approval voting just moves the spoiler effect into how people vote

that's orthogonal. ranked voting methods already have (arguably more severe) response to strategic voting AND ALSO can fail IIA even with no strategy applied, just by changing an irrelevant alternative.

> Personally I think the possibilities of circular ties under Ranked Pairs is oversold.

what does that even mean? we have VSE figures that measure the combined effect of all failures, including when the Condorcet winner isn't the favorite candidate of the electorate (not the social utility maximizer). https://electionscience.github.io/vse-sim/vse-graph.html

that's not under or oversold, it's just measured performance.

[mindslight]

Restating my disclaimer of "It's been a while since I've studied the details of voting systems"...

> ranked voting methods ... can fail IIA even with no strategy applied, just by changing an irrelevant alternative.

Can you clarify whether you're referring to some ranked methods (eg IRV), or all ranked methods (ie including ranked pairs) ?

> that's not under or oversold, it's just measured performance.

Isn't this due to defining "performance" in a way that is congruent with Approval (/ Score) ? A quick skim of that VSE page has it talking about "utility", which I would imagine is a scalar per candidate representing "happiness" ?

The problem I have with Approval is that coming from our two-terrible-party system - do I Approve my latent terrible party or not? That choice seems purely down to strategy, compared to being able to rank them to say I completely prefer the new party/candidate over my latent terrible party, and my latent terrible party over the other latent terrible party. The dynamic also seems exacerbated knowing there will be a lot of people who continue to vote exactly as they did under plurality.

[ClayShentrup]

it's mathematically proven that all ranked methods can fail IIA. see arrow's theorem.

> Isn't this due to defining "performance" in a way that is congruent with Approval (/ Score)

1. i did not define performance in a way that is congruent with approval/score. scores are not utilities. they are the modification of utilities via ignorance, normalization, and strategy.

2. that the correct social welfare function is just the sum of all voter utilities (the definition of "performance") is mathematically proven. https://www.rangevoting.org/UtilFoundns

> do I Approve my latent terrible party or not?

this is not a "problem". it's well understood. https://www.rangevoting.org/RVstrat6

approval voting obliterates IRV ("RCV") with any mixture of strategic or honest voters, so i'm not sure why you're bringing up strategy. https://www.rangevoting.org/StratHonMix

[ClayShentrup]

i had a chance to visit arrow at his palo alto condo circa 2014. his theorem is nice and all, but it only makes sense to apply it to social welfare functions, not voting methods. yes, the correct social welfare function is just the utilitarian sum of all voters' individual utilities.

https://www.rangevoting.org/UtilFoundns

once you know that, that's the function you use in your VSE metrics. then the performance of the voting method is measurable without having to think about any specific criteria.

https://www.rangevoting.org/PropDiatribe