[EM] Why I Prefer IRV to Condorcet

[Juho Laatu]

--- On Sat, 22/11/08, Greg <greg at somervilleirv.org> wrote:

> Perhaps intuitiveness is a bit in the eyes of the beholder,
> but I'll
> tell you the strategies I find intuitive:
> 
> - Burying a candidate with strong first choice support

Yes. This is close to the case that I discussed.
I didn't assume strong first choice support but
just any strength (e.g. being close to a Condorcet
winner).

> - Bullet voting for a candidate with strong first choice
> support

Yes. (Also any other strength ok, or one could
bullet vote one's own not-so-strong favourite.)

> - A compromise in which you switch your first choice vote
> to a
> candidate who has stronger first choice support.

Yes. (Again strong first choice support typical
but not necessary.)

> 
> From anecdotal personal experience, I actually think
> burying might be
> the most intuitive of them all.

Yes, may be.

> Almost every university
> election I
> voted for as an undergraduate used IRV. After each one,
> there was
> often a person here or there who claimed to have voted for
> one
> front-runner and buried the other front-runner on their
> ballot, not
> aware that this had no effect on the outcome. Now, as I go
> around
> teaching IRV to people, there's often some guy who
> thinks he's clever
> who brings up the idea of burying (though he doesn't
> know the term
> "bury"), thinking he's discovered some sort
> of flaw; that is, until I
> correct him.

One problem (or actually a good thing) with
strategies is that if there are strategies they
may not always be rational. In such a situation
hopefully we can recommend sincere voting to
all voters as a better alternative to confused
use of various strategies.

> 
> It is from this personal experience that I have grown to
> believe
> resistance to burying essential. Again, this is purely
> anecdotal, and
> empirical research in this area would be helpful.

It is very difficult to defend against widespread
irrational use of strategies. Recommending sincere
voting may be a good approach. (Maybe people will
learn after spoiling some election and electing
some clearly unwanted candidate as a result of
burying all the reasonable competitors :-) .)

Juho


> 
> Greg
> 
> 
> On Sat, Nov 22, 2008 at 5:53 AM, Juho Laatu
> <juho4880 at yahoo.co.uk> wrote:
> > Yes, it is not intuitive to abandon one's
> favourite. What is then intuitive? Burying as a Condorcet
> strategy is certainly not intuitive (quite difficult to
> understand even to experts). Burying in the sense of ranking
> the strongest competitor of one's favourite potential
> winner last may be intuitive to many.
> >
> > Since in Condorcet there are some situations where
> burying is a working strategy, this property (if advertised)
> may encourage people to (irrationally) bury (or rank the
> competitors last) even more generally. In IRV voters may
> also intuitively bury although that doesn't make much
> sense.
> >
> > In Condorcet one would thus have to trust
> "political advisers" to tell when to bury (to make
> the strategy rational). Similarly in the example that I gave
> the voters would maybe have to be reminded that it could be
> wise to compromise this time.
> >
> >
> >
> > Although all the three factions are large the B
> supporters may see C as a spoiler. If C would not
> participate both B and C supporters would be happier with
> the outcome. (C thus spoils the result also from the C
> supporters' point of view.)
> >
> > In the example B and C could be candidates of the same
> party. Then nominating also C (the more extreme of the two
> potential candidates) was maybe a mistake.
> >
> > Juho
> >
> >
> >
> > --- On Sat, 22/11/08, Greg
> <greg at somervilleirv.org> wrote:
> >
> >> From: Greg <greg at somervilleirv.org>
> >> Subject: Re: [EM] Why I Prefer IRV to Condorcet
> >> To: juho4880 at yahoo.co.uk
> >> Cc: election-methods at lists.electorama.com
> >> Date: Saturday, 22 November, 2008, 10:04 AM
> >> Yes, this is as intuitive as it comes in terms of
> IRV
> >> strategy, but I
> >> still find it ultimately counter-intuitive for the
> average
> >> voter.
> >> Candidate C has a the second-most number of first
> choices,
> >> which
> >> likely corresponds to the second-biggest campaign
> >> (second-most amount
> >> of money, volunteers, name recognition, exposure,
> ads,
> >> etc). The
> >> thought of abandoning C in favor of B, who will
> probably
> >> have a
> >> smaller campaign (less money, fewer volunteers,
> etc), I
> >> think will
> >> strike the average voter as counter-intuitive. In
> these
> >> respects, this
> >> scenario is quite unlike the standard spoiler
> scenario,
> >> where the
> >> incentive is to intuitively switch one's vote
> from the
> >> smaller to the
> >> bigger campaign. Nevertheless, I would agree that
> it's
> >> something to be
> >> on the lookout for as IRV spreads.
> >>
> >> Greg
> >>
> >>
> >> On Sat, Nov 22, 2008 at 2:00 AM, Juho Laatu
> >> <juho4880 at yahoo.co.uk> wrote:
> >> > Here's one IRV example with three strong
> >> candidates and where voters do have some incentive
> to
> >> compromise.
> >> >
> >> > 45: A>B>C
> >> > 10: B>A>C
> >> > 15: B>C>A
> >> > 30: C>B>A
> >> >
> >> > We have one centrist candidate (B) between
> two others.
> >> >
> >> > According to this poll it seems that B will
> be
> >> eliminated first, and then A would win since some
> B
> >> supporters prefer A to C.
> >> >
> >> > If sufficient number of C supporters would
> abandon
> >> their favourite and vote B>C>A, then C would
> be
> >> eliminated first and the centrist candidate B
> would be
> >> elected.
> >> >
> >> > Based on this poll it seems that if C voters
> don't
> >> compromise (or if C will not withdraw) then from C
> >> supporters' point of view the worst candidate
> (A) will
> >> be elected.
> >> >
> >> > - This situation could be reasonably common
> (or
> >> plausible) in real life
> >> > - B is a Condorcet winner ((that IRV would
> not elect))
> >> > - B seems to be politically closer to C than
> to A
> >> > - C is not a weak candidate since with few
> more
> >> "core" voters or second place support it
> could
> >> beat A (if the strong centrist candidate B will be
> >> eliminated first)
> >> >
> >> > C supporters could be optimistic and hope for
> a change
> >> in opinions before the election day. I mean that
> in real
> >> elections many voters may be optimistic and
> fighting
> >> spirited and believe rather in those earlier polls
> that gave
> >> their favourite more votes than this poll etc.
> >> >
> >> > The strategy of the C voters is not very
> >> "intuitive" in the sense that it is
> never natural
> >> to abandon one's favourite (it could be easier
> e.g. to
> >> rank the strongest competitor last even if that
> would be an
> >> irrational strategy). But on the other hand it is
> quite
> >> straight forward to see from the poll results
> (maybe voiced
> >> out by media) that indeed it makes sense for the C
> >> supporters to give up and abandon C if people will
> vote as
> >> indicated in this poll. The voters will thus have
> a dilemma,
> >> whether to vote sincerely or whether to
> compromise.
> >> >
> >> > Juho
> >> >
> >> >
> >> >
> >> > --- On Sat, 22/11/08, Greg
> >> <greg at somervilleirv.org> wrote:
> >> >
> >> >> From: Greg <greg at somervilleirv.org>
> >> >> Subject: Re: [EM] Why I Prefer IRV to
> Condorcet
> >> >> To: election-methods at lists.electorama.com
> >> >> Date: Saturday, 22 November, 2008, 3:06
> AM
> >> >> Thanks, Chris. I'll correct the
> errors and
> >> rephrase some
> >> >> things I
> >> >> didn't say correctly.
> >> >>
> >> >> On the Compromise strategy, I think some
> >> compromises are
> >> >> more
> >> >> intuitive than others. I think it's
> intuitive
> >> to
> >> >> abandon a more weakly
> >> >> supported candidate, e.g. Nader, in favor
> of a
> >> major
> >> >> candidate, as is
> >> >> common in FPTP. But it strikes me as more
> >> >> counter-intuitive, at least
> >> >> for the average voter, to abandon a
> candidate with
> >> strong
> >> >> core support
> >> >> in favor of a more weakly supported
> candidate, as
> >> could
> >> >> happen under
> >> >> IRV. Then there's the issue as to
> whether the
> >> result of
> >> >> the
> >> >> strategizing is a better or worse result
> overall .
> >> . . but
> >> >> that's a
> >> >> tricky topic for another time.
> >> >>
> >> >>
> >> >> > Date: Thu, 20 Nov 2008 11:51:01
> -0800 (PST)
> >> >> > From: Chris Benham
> >> <cbenhamau at yahoo.com.au>
> >> >> > Subject: [EM]  Why I Prefer IRV to
> Condorcet
> >> >> >
> >> >> > Greg,
> >> >> > I generally liked your essay. I rate
> IRV as
> >> the best
> >> >> of the single-winner methods that
> >> >> > meet Later-no-Harm, and a good
> method (and a
> >> vast
> >> >> improvement on FPP).
> >> >> >
> >> >> > But I think you made a couple of
> technical
> >> errors.
> >> >> >
> >> >> > "However, because bullet voting
> can help
> >> and
> >> >> never backfire against one's top
> choice under
> >> >> > Condorcet, expect every campaign
> with a shot
> >> at
> >> >> winning to encourage its supporters to
> >> >> > bullet vote. "
> >> >> >
> >> >> > Bullet voting can "backfire
> against
> >> one's top
> >> >> choice under Condorcet" because
> Condorcet
> >> >> > methods, unlike IRV, fail
> Later-no-Help.
> >> >> >
> >> >> >
> >> >>
> >>
> http://groups.yahoo.com/group/election-methods-list/files/wood1996.pdf
> >> >> >
> >> >> > In this 1996 Douglas Woodall paper,
> see
> >> "Election
> >> >> 6" and the accompanying discussion
> on
> >> >> > page 5/6 of the pdf (labelled on the
> paper as
> >> >> "Page 13").
> >> >> >
> >> >> > Quoting again from your paper:
> >> >> > "As mentioned, every voting
> system is
> >> >> theoretically vulnerable to strategic
> >> manipulation, and IRV
> >> >> > is no exception. However, under IRV,
> there is
> >> no
> >> >> strategy that can increase the likelihood
> of
> >> >> > electing one's first choice
> beyond the
> >> opportunity
> >> >> offered by honest rankings. While there
> are
> >> >> > strategies for increasing the
> chances of less
> >> >> preferred candidates under IRV, like
> push-over,
> >> >> > they are counter-intuitive."
> >> >> >
> >> >> > The Push-over strategy is certainly
> not
> >> limited to
> >> >> improving the chance of electing a
> "lower
> >> >> > [than first] choice". Say
> sincere is:
> >> >> >
> >> >> > 49: A?
> >> >> > 27: B>A
> >> >> > 24: C>B
> >> >> >
> >> >> > B is the IRV winner, but if? 4-21
> (inclusive)
> >> of the A
> >> >> voters change to C or C>? then the
> winner
> >> >> > changes to A.
> >> >> >
> >> >> > But as you say the strategy
> isn't
> >> >> "intuitive" , and backfires if
> too many
> >> of the A
> >> >> supporters try it.
> >> >> > Some IRV opponents claim to like
> Top-Two
> >> Runoff, but
> >> >> that is more vulnerable to Push-over
> >> >> > than IRV (because the strategists
> can support
> >> their
> >> >> sincere favourite in the second round).
> >> >> >
> >> >> > The quite intuitive strategy that
> IRV is
> >> vulnerable to
> >> >> is Compromise, like any other method that
> >> >> > meets Majority. But voters'
> incentive to
> >> >> compromise (vote one's front-runner
> >> lesser-evil in first
> >> >> > place to reduce the chance of
> front-runner
> >> >> greater-evil winning) is generally vastly
> vastly
> >> less
> >> >> > than it is under FPP.
> >> >> >
> >> >> > (There are methods that meet both
> Majority
> >> and
> >> >> Favourite Betrayal, and in them
> compromisers
> >> >> > can harmlessly vote their sincere
> favourites
> >> in
> >> >> equal-first place.)
> >> >> >
> >> >> > But some Condorcet advocates are
> galled? by
> >> the
> >> >> Compromise incentive that can exist where
> >> >> > there is a sincere CW who is not
> also a
> >> sincere Mutual
> >> >> Dominant Third winner.
> >> >> >
> >> >> > 49: A>B
> >> >> > 02: B>A
> >> >> > 22: B
> >> >> > 27: C>B
> >> >> >
> >> >> > On these votes B is the CW, but IRV
> elects
> >> A.? If the
> >> >> C>B voters change to B then B will be
> >> >> > the voted majority favourite, so of
> course
> >> IRV like
> >> >> Condorcet methods and FPP will elect B.
> >> >> >
> >> >> > Chris Benham
> >> >> ----
> >> >> Election-Methods mailing list - see
> >> >> http://electorama.com/em for list info
> >> >
> >> >
> >> >
> >> >
> >> >
> >
> >
> >
> >
> >