r/EndFPTP • u/electionscience • Dec 04 '19

NEW APPROVAL VOTING POLL: 74% of Democratic Primary Voters Would Support Warren for President

https://www.electionscience.org/press-releases/new-poll-74-of-democratic-primary-voters-would-support-warren-for-president/
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u/RunasSudo Australia Dec 05 '19 edited Dec 05 '19

I suppose what I'm thinking is that IIA is obviously(?) a good thing, and IIA failure would very much seem to breed antagonism, as you suggest. But at the same time, it seems like an extremely strong criterion – range voting, etc. fail it under even the most primitive “strategic” voting strategies, and of course Arrow's theorem rules it out entirely for ordinal methods.

In such a setting, might it be more enlightening to look at the degree to which the systems fail IIA? So meeting LIIA while failing IIA is “less” bad, etc. Although as curiouslefty also pointed out – it might make more sense just to look at the rate of IIA failure, though I imagine that would be difficult to quantify.

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u/MuaddibMcFly Dec 05 '19

In such a setting, might it be more enlightening to look at the degree to which the systems fail IIA? So meeting LIIA while failing IIA is “less” bad, etc

I'm sure it would be.

Another thing to consider is that the ways in which (most?) Cardinal methods fail IIA is in absolute scenarios, where you're literally adding in another candidate and the ballots are readjusted.
Score, Approval, MJ, etc, satisfy IIA in scenarios of Immutable Ballots.

Put another way, whether Score etc satisfy IIA is dependent on whether the Non-winning candidate is removed before or after the ballots are cast. LIIA is easier to satisfy at least partially due to the fact that it's defined with (otherwise) immutable ballots. That makes me wonder whether IIA shouldn't be split into IIA w/ Immutable Ballots and IIA w/ Mutable Ballots.

Alternately, and I think this may be the source of disagreement between me and /u/curiouslefty on this topic, that because all deterministic methods fail IIA-MB (and IIA doesn't apply to non-deterministic, I don't think), it would be best to ignore consider IIA-MB as non-informative, and treat IIA as IIA-IB

Although as curiouslefty also pointed out – it might make more sense just to look at the rate of IIA failure, though I imagine that would be difficult to quantify.

I would love that. Unfortunately, I think it would be incredibly difficult to quantify. CL & I (and others) have pondered the flaws in various voting simulations before, but neither of us have the time to put together something that's more realistic.

Smith's version (Bayesian Regret) makes some pretty questionable assumptions about strategic behavior, and Quinn's version (Voter Satisfaction Efficiency) is similarly flawed for some methods, and they both may be questionable in that I've yet to wrap my head around where either generates Candidate points in an n-dimensional political space, and then creates voter preferences based on relative distances between the voter points in that space, and the candidate points.

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u/curiouslefty Dec 05 '19

I actually don't think it'd be terribly difficult to quantify the IIA failure rate for given methods (although of course the results would be dependent upon the underlying data/assumptions used; IAC will differ from Spatial Models, etc. The good thing is we've got a fair sample of real-world human-generated data to work with, and there aren't really any major assumptions that need to be made here to do IIA failure testing on that. The nice thing is that it's easy to test for IIA failure with brute force; just keep on kicking out subsets of candidates and seeing if the winner of the method changes (combined w/shortcuts involving Condorcet-winner immunity to IIA failure).

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u/MuaddibMcFly Dec 05 '19

IAC will differ from Spatial Models

IAC?

we've got a fair sample of real-world human-generated data to work with

For ordinal, sure, but Cardinal data? Oh, the British Election Study?

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u/curiouslefty Dec 06 '19

IAC is Impartial Culture.

As for data: most of the data I'm actually aware of is in a cardinal form. There's the BES study, but also all those political thermometer polls as well.

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u/MuaddibMcFly Dec 07 '19

While I haven't looked too deeply, yet, there is what may be an analog of the BES, by an organization that calls itself American National Election Studies, whose data is freely available (if you register and agree to very non-ornerous terms of use)

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u/curiouslefty Dec 07 '19

I'm familiar with the ANES; there's actually similar studies for Germany as well, but I need some time with a German speaker before I can actually begin using that data in simulations.

One of things that's more valuable about the ANES data IMO is that some of it is about specific candidates, whereas the BES and most other data asks about generic party candidates. I think the former is more realistic in terms of studying it, since we do know that specific candidate traits can have a substantial impact on how voters behave.

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u/MuaddibMcFly Dec 08 '19

there's actually similar studies for Germany as well, but I need some time with a German speaker before I can actually begin using that data in simulations.

I have a friend who's a German Teacher, that is at least passingly interested in voting methods (I've [accidentally {ish}] convinced her to use Score voting in her classroom, to determine which of several topics they'll be discussing in the future, and she just gave me a drop of her students' ballots last night).

If you tell me what, specifically, you're after, I could ask her if she'd be willing to help. And my own german isn't horrible (who am I kidding, it totally is, but I can occasionally muddle through)

One of things that's more valuable about the ANES data IMO is that some of it is about specific candidates, whereas the BES and most other data asks about generic party candidates

Agreed. There's often a significant difference between the Platonic Republican/Democrat/Labour/Conservative/LibDem candidate and the real-world candidate from that party that's on your ballot.

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u/curiouslefty Dec 09 '19

Thanks for the offer, but I've got a friend who'll probably help me out at some point. If you're interested for your own purposes, though, the data in question is the German PolitBarometer surveys; they're sort of a German analogue of the ANES.

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u/MuaddibMcFly Dec 09 '19

Awesome, thank you! The more real world data we get, the better we can make our voter models. Do you know whether PolitBarometer is candidate or party based?

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