[EM] Technical nomenclature regarding voting systems.

[Andy Dienes]

Other scholarly terms for "avoid strategic behavior" might be to describe
the mechanism as "incentive compatible" or "strongly/weakly truthful."

On Wed, Feb 16, 2022 at 7:21 AM Kristofer Munsterhjelm <km_elmet at t-online.de>
wrote:

> On 16.02.2022 08:48, robert bristow-johnson wrote:
> > In my paper:
> >
> > The Failure of Instant Runoff Voting to accomplish the very purpose
> > for which it was adopted: An object lesson in Burlington Vermont
> >
> >  https://drive.google.com/file/d/1jIhFQfEoxSdyRz5SqEjZotbVDx4xshwM/view
> >
> > I wanted to boil down the Burlington 2009 IRV failure to these two
> principles:
> >
> >    (1) One person, one vote
> >    (2) Majority rule
> >
> > and these three desirable properties of elections:
> >
> >    (3) Avoid spoiler effect
> >    (4) Disincentivize tactical voting
> >    (5) Precinct summability
> >
> > I believe that (1) is called the "Principle of Anonymity" in
> > scholarly circles, that (2) (as stated in the paper) is the
> > "Condorcet Criterion", and that (3) is "Independence of Irrelevant
> > Alternatives" (I am of the school that says *any* loser that changes
> > the winner is a spoiler, not just losers that have no chance of
> > winning.)
>
> There are two "shouldn't matter who you are" criteria. There's
> anonymity, which means that there are no privileged voters; and there's
> neutrality, which means that there are no privileged candidates. For
> instance, the Ranked Pairs version where you set a tiebreaker first
> violates neutrality, because the candidate who's first on the tiebreaker
> has an advantage simply due to who he is. A method that lets the chair's
> vote count double violates anonymity.
>
> Strictly speaking, IRV passes both of these. I think you need something
> that's more about the relative power of a vote, so that you could
> capture the problem of IRV ignoring some votes' later preferences while
> accepting others'. But I don't know of any term that captures this well.
>
> > (5) is simply about Process Transparency, an important principle of
> > fair and honest elections.
> >
> > Is there a better or a more scholarly label for Property (4)?  In my
> > paper I describe (4) as:
> >
> > 4. Voters should not be called upon to do “tactical voting”. Voters
> > should feel free to simply vote their conscience and vote for the
> > candidates they like best, without worrying about whom that they think
> > is most electable... They should not have to sacrifice their vote for
> > their favorite choice because they are concerned about “wasting” their
> > vote and helping elect the candidate they loathe. Voters should be able
> > to “Vote their hopes rather than vote their fears”.
> >
> > Is there a technical name for (4)?  Would it be "Favorite Betrayal"?
>
> Favorite betrayal is one kind of protection from strategic voting. It
> basically says "you never need to do a compromising strategy". There are
> others, like in Plurality or IRV where you never need to do a burial
> strategy.
> It's not possible for a deterministic ranked voting method to be
> completely free of the need to use strategy, and the reason is actually
> related to IIA.
>
> So a method that passes IIA more often should be less susceptible to
> strategy. And James Green-Armytage found that making a method Condorcet
> compliant never increases the number of times that strategy pays off (if
> that method is of a form that a coordinated majority can always force an
> outcome).
>
> "Voting your hopes rather than your fears" sounds like immunity to
> compromising. If that's right, then favorite betrayal is indeed what you
> want. Condorcet methods can't pass this criterion, but some methods come
> very close. (And every Condorcet method passes it when there's a honest
> CW and the strategists can't engineer a cycle.)
>
> But for the more general concept, I don't think there is one. You could
> say "strategy-proofness" or the method being strategy-proof -- that's
> the closest you can get, I think.
>
> -km
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