[EM] Strategy-free criterion

[Kevin Venzke]

Hi CLC,

>> Something I will have to post about at some point is what a game-changer it
>> is if we take it as an assumption that elections will have two frontrunners
>> and all voters use frontrunner truncation strategy. Arbitrary-looking majority
>> rules prove very useful in maximizing performance.
> 
> I think there's a big issue with assuming two frontrunners because A) in that case,
> it's just a majority vote between them and B) you can have situations where
> multiple candidates have strongly correlated scores, e.g. if they're all from the
> same party.

It seems like you think I meant that a method identifies the frontrunners. It could
try, but that isn't inherent to what I'm saying. I'm talking about an assumption
about the environment methods will run in. And I don't propose any assumptions
about how the perceived frontrunners are chosen.

> This is why I previously suggested that, ideally, a system should satisfy both
> zero-info honesty and LNHe+FBC. This seems like the maximally-honest combination
> of properties, because it handles low-information elections honestly, and
> high-information elections "as sincerely as possible" (i.e. no order-reversal,
> which is enough to guarantee the Condorcet winner is visible from the ballots).

I am curious what your definition of "visible from the ballots" is. It's possible
to generate scenarios where the sincere CW is one of two frontrunners and yet still
loses under practically all methods, because they lose necessary support (from
truncation) from supporters of the other frontrunner while most of the CW's
supporters actually prefer a different candidate to the CW.

> STAR works off of a very similar principle. The hope is the first stage will find
> two similar frontrunners, and then the second stage is strategyproof (since it's a
> majority vote). This combination fails both criteria in theory, but might satisfy
> them in practice. That's especially true if you combine it with other improvements:
> countbacks, a master lever for straight-ticket voting, and skipping the runoff if
> the top-two finishers are from different parties could maximize the chances of
> STAR working as it should.
> 
> I think the best hope for a system that formally satisfies both criteria is
> probably somewhere in the generalized median family of voting methods.

That would surprise me, but who knows.

Kevin
votingmethods.net