[EM] IRV and Brown vs. Smallwood

[Juho Laatu]

One more observation about the strategy and
long term promotion of candidates.

In the polls before the election the voters
may mark all the candidates but in the actual
election they may leave out some favourites
with no chances to win in order to make sure
that their vote will not harm their favourite
candidates with chances to win.

Some votes may use the strategy when it is
needed. Some voters may use it always
(safely). Some voters may never use it. In
the presented example such a mixture of
voting behaviour would guarantee that the
radical candidates will be eliminated early
enough not to spoil the election from their
supporters' point of view.

Some information is lost in the actual
election but if there are good polls that
information may be readable there (and new
candidates will get publicity that way and
their viability will be considered before
voters decide whether to rank them in the
actual election. Long term promotion of
candidates may thus still work and new
entrants may grow even if the strategy is
actively followed.

If one wants to get full rankings also in
the actual election one could use such IRV
variants where this problem is not too bad.
I sometimes proposed forcing voters to
approve more and more candidates when their
first candidates are too weak. No candidates
are eliminated from the race, so they may
"come back" if they have lots of secondary
support (like the moderate candidates in the
example).

The described strategy may not materialize
very strongly in real life since voters
often are quite eager to support their first
preference candidates. But as already noted
in some scenarios (like in the example) it
would be better to apply the strategy since
using the wrong strategy (sincerity) may
lead to a bad outcome that may be clearly
visible (especially if the votes will be
published). (Alternatively some variants of
IRV could be used.)

Juho


--- On Thu, 9/4/09, Juho Laatu <juho4880 at yahoo.co.uk> wrote:

> Sorry, fifth line was wrong, should be:
> 
> 25: Dr>Dm>Rm>Rr
> 20: Dm>Dr>Rm>Rr
> 05: Dm>Rm>Dr>Rr
> 05: Rm>Dm>Rr>Dr
> 20: Rm>Rr>Dm>Dr
> 25: Rr>Rm>Dm>Dr
> 
> Juho
> 
> 
> --- On Thu, 9/4/09, Juho Laatu <juho4880 at yahoo.co.uk>
> wrote:
> 
> > From: Juho Laatu <juho4880 at yahoo.co.uk>
> > Subject: Re: [EM] IRV and Brown vs. Smallwood
> > To: election-methods at lists.electorama.com
> > Date: Thursday, 9 April, 2009, 7:39 PM
> > 
> > --- On Thu, 9/4/09, Kristofer Munsterhjelm <km-elmet at broadpark.no>
> > wrote:
> > 
> > > Juho Laatu wrote:
> > > 
> > > > Actually it may be a quite good strategy in
> > > > IRV not to rank those favourite candidates
> > > > that do not have a chance but to rank only
> > > > those candidates that have a chance. This
> > > > increases the probability that one's most
> > > > favoured candidates with chances of winning
> > > > the election are not eliminated too early
> > > > (assuming that they might win if they could
> > > > stay in the race until the end).
> > > 
> > > That's also the strategy in Plurality - don't
> vote
> > for
> > > those candidates that don't have a chance. But
> if
> > everybody
> > > thinks like this, you end up with the "lesser of
> n
> > evils".
> > 
> > Yes, it is true that if people do not rank
> > the lesser candidates they will never grow
> > and become major candidates. It may be more
> > important for many to try to influence the
> > future elections than to try to eliminate
> > some small risks in this election. And of
> > course in many cases one can vote also for
> > the lesser candidates without problems. The
> > described strategy is just a safe bet that
> > eliminates risks in these elections.
> > 
> > (Psychological factors are an important
> > topic that should be covered too.)
> > 
> > > One of the points of ranked voting is that you
> don't
> > have to
> > > do that - you can vote X > Y > Z so you say
> "I
> > like X,
> > > but if I can't have X, I'd have Y before Z".
> > 
> > It seems that in IRV it is the safest
> > strategy not to rank the weak candidates
> > (if one only aims at winning this election
> > in question), but not a necessary strategy
> > for all situations to guarantee an optimal
> > vote.
> > 
> > >    If this ability
> > > is compromised by that voting for unpopular
> > candidates
> > > dilutes the vote so much one should rather not,
> then
> > why
> > > have ranked voting in the first place?
> > 
> > Words "so much" are important. Polls are
> > inaccurate, people do believe in the
> > chances of their favourites, there will be
> > changes in support, there is a need to
> > show support to the "so far unpopular"
> > candidates, and the risks involved in this
> > strategy may be small. As a result I don't
> > think people should and people will apply
> > this strategy generally in IRV elections..
> > 
> > There are however cases where the risks
> > are very real. The original example was
> > one. Here is another with moderate and
> > radical Democrats and Republicans.
> > 
> > Approximate support:
> > 25: Dr>Dm>Rm>Rr
> > 20: Dm>Dr>Rm>Rr
> > 05: Dm>Rm>Dr>Rr
> > 05: Rm>Dm>Rr>Dr
> > 05: Rm>Rr>Dm>Dr
> > 25: Rr>Rm>Dm>Dr
> > 
> > In this example all four candidates have
> > the risk of being eliminated early. If Dm
> > or Rm will be eliminated first then the
> > other party is likely to win. It makes
> > sense to the Dr and Rr supporters not to
> > rank their favourite first (although they
> > are about as popular within the party as
> > the other moderate candidate).
> > 
> > (From this point of view Condorcet methods
> > allow the voters to use more sincere
> > rankings than IRV.)
> > 
> > Juho
> > 
> > 
> > 
> > 
> > 
> > 
> >       
> > 
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> > 
> 
> 
>       
> 
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