[EM] Realistic strategy questions

[Jameson Quinn]

Omnibus response:

Toby: "Which voting systems?"

At present: plurality, IRV, borda, ranked pairs, range, MAV (a graded
median/Bucklin system), approval. The code is on
github<https://github.com/The-Center-for-Election-Science/vse-sim> (in
Python 3), so anyone is free to add systems.

Steve: "Coordinated strategic?"

That's what I'm calling cliquishness. Even if I set it to a pretty high
number, like 70%, there will still be plenty of scenarios where the
strategy on both sides is balanced.




2014-02-24 15:30 GMT-05:00 Kevin Venzke <stepjak at yahoo.fr>:

> Hi Toby,
>
> In my own simulations (in which voting blocs learn how the method works
> through repeated polls, until ultimately one poll becomes the election
> result) the consistent difference between WV and margins was favorite
> betrayal (i.e. WV sees compression incentive where margins sees compromise
> incentive). IIRC the two usually scored pretty similarly with regard to
> sincere CW election rate and "utility maximizer" election rate.
>
> Actually, I found most methods pretty hard to differentiate wrt social
> utility. Given the vast range of possible underlying voter utilities, I
> think the actual voter utilities are very hard to perceive, even if the
> (strategic) votes aren't very distorted from the truth.
>
> Jameson, does your strategy #3 "fully strategic" mean Warren-style "use
> favorite betrayal and burial no matter what"? Or is it more of an
> approval-style "everybody gets an A or an F" thing, under the methods that
> allow it at least?
>

In strictly ranked Condorcet, it means FB and burial. In non-strict
ranking, I think it should be just FB (for margins) or just turkey-raising
(for WV), that is, compression-to-ties on one side, and inversion on the
other. But I'm open to suggestions on that count.


>
> Does your polling system do a round of Range voting, or something like
> that?
>

A round of honest votes, using the same system. In some scenarios, those
honest results are then subjected to a media bias which disfavors arbitrary
"non-major" candidates according to one of two soft scales.


>
> My concern would of course be the possibility of supposing behavior that
> doesn't happen to make sense in a specific scenario. I see that you have
> some conditions to try to avoid this. But naturally if "strategic" voters
> strategize poorly (either too much or too little, or not in the right way)
> or "unevenly" poorly (among the various methods and scenarios) this could
> bias a method's final score (either positively or negatively!).
>

Right. My goal is to find some set of models (each of which is a
probability measure over scenarios) that I can call "realistic", and
explore relative system quality under such models. So I'm not aiming for
ideal strategy, except insofar as there are significant numbers of
real-world voters who strategize ideally.

Jameson
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