On Apr 10, 2010, at 12:39 AM, Kevin Venzke wrote:
Hi Juho,
--- En date de : Ven 9.4.10, Juho <juho4...@yahoo.co.uk> a écrit :
I more or less despise the election of A in
this
scenario:
49 A
24 B
27 C>B
I believe the possibility of this outcome is
a
disincentive for a candidate
like C to run.
The story behind these votes seems to be that C
is
ideologically close to B and its nomination makes
A win
instead of B. If C is ideologically close to B why
don't the
"B" voters vote "B>C" (and make C win)?
Because the story is that C is not considered an
established candidate
(or a frontrunner), and the B voters (if they actually
prefer C, which
is not something I mean to suggest) will not
condescend to rank C.
Depending on the method, they could hand the election
to C by ranking C,
and/or alternatively compel C supporters to not vote
sincerely.
Ok, but the story is not quite flawless yet.
Case 1: "B" voters did not notice C. B had 51 supporters
before the nomination of C. All that heard of C changed
their opinion to "C>B". If C is so obviously better than
B then also some of the "A" voters should have voted
"A>C" (or "A>C" if they feel the other way around for
some reason). But it seems that also they did not notice C.
It is also strange that someone can get 27% support (clearly
more support than B) and still be unknown to so many of the
voters.
Case 2: "B" voters did notice C and liked C but didn't want
to vote for C. In this case the votes are not sincere but
twisted for some psychological reasons. (Also some part of
"A" voters should have ranked B or C if they noticed C.)
I don't get why people assume that B voters secretly do like C. If I
vote for a left-wing candidate, that doesn't mean I like all left-wing
candidates better than all right-wing candidates.
I don't want to make assumptions in one way or another but I'd like to
identify some rational explanation to why people voted as they did.
This is needed also in order to evaluate if the outcome that the
method produces is acceptable or not. The example (at least at first
sight) seems to suggest that B and C are close to each others since
all the C supporters liked B more than A. I discussed shortly also
another natural and simple looking (linear opinion space based) option
where C is e.g. clearly to the left of B. In this case the B
supporters might think A=C (or split their preferences between these
two) but in that case the A supporters (maybe right wing) could think
more B>C than they now did.
Yes, you are right: I am proposing that voters backing more
established
candidates may insincerely decline to give lower preferences to other
candidates. But this isn't simply because they are mean. It benefits
candidates like B if the nomination of candidates like C risks
wrecking
the result from the perspective of C voters.
Yes, established parties/candidates may do all they can (including
psychological games and giving impression that the new parties/
candidates are irrelevant) to avoid new parties/candidates becoming
serious contenders.
It seems that the role of non-informed voters and/or
non-sincere/mutinous voters and the surprising emergence of
candidate C have a strong role in the story, and all the
blame (of not following the story (and intended outcome)
that was discussed above) can not be put on margins alone.
I don't understand that way of thinking. Uncertainty about the
strength
of a candidate is going to exist everywhere. Self-interested strategy
is going to exist everywhere. I guess you could excuse margins from
messing up here, but what's the point?
Yes, there will be considerable uncertainty. In the light that the key
story behind these votes is that there are two established parties who
want to keep the third parties out, my concern was that the supporters
of those parties seem to have a strategy that influences the outcome.
If in that situation margins leads to an outcome that some of these
strategists do not like, that could be also a positive thing in the
sense that maybe in the next elections those voters would not apply
the same strategy (i.e. do all they can to make third party candidates
look insignificant).
In this example the B supporters that felt C>A (but did not vote so)
should have voted or could vote next time B>C. Also other A and B
supporters could reconsider if bullet voting is what they should do.
I'm aware you can find scenarios where WV offers a strategic incentive
where margins doesn't. I don't think I've seen theories about general
patterns of this, or any particularly relevant and alarming scenarios,
etc.
I believe there are also situations where WV in practice (not only in
some theoretical scenarios) is more vulnerable. I however tend to
think that in real life large public elections all Condorcet methods
are quite good and not very vulnerable to strategies. That is why I
put also considerable weight on how WV and margins perform with
sincere votes. Also on this side I believe there are real life
situations where WV gives worse results. The example that you gave
suggests that there are also scenarios where margins performs worse
with sincere votes than WV does, and I tried to analyze if the
described scenario may happen in real life in the and if the result is
not the best possible.
Here are also some example scenarios FYI.
- A simple WV strategic vulnerability example. Sincere: 49:A, 49:B>C,
1:C>B. B wins. Strategic: 49:A, 49:B>C, 1:C>A. C wins.
- Another related but maybe more real life like example with richer
variation of votes: 10:A, 22:A>B, 17:A>C, 28:B>C, 23:C>B. B wins. Both
A wing and BC wing think that B is better than C. If you add three
more (sincere or strategic) C>A votes then C wins in WV.
The best scenario is for C to be able to run, be voted
for sincerely, and
either win, or not affect the outcome at all.
Yes, that would be ideal.
If C is
ideologically far from B then most "B" voters may
vote as
they do now, but then maybe "A" voters should vote
"A>B"
(and make B win) (since C seems to be closer to B
than A).
It is hard to find an explanation to sincere votes
like
this. Or are these maybe strategic votes, e.g. so
that
sincere "A>B" voters have decided to vote "A"?
The A voters will not vote A>B because A and B are
considered the
frontrunners. (i.e. that is the scenario that concerns
me.)
Yes but also this means that "A" voters are badly
misinformed when none of them have heard of C or believe
that C is weak although C has 27% first place support
(clearly more than B) and all that heard of C "on the B
side" voted for C.
You keep saying 27 is clearly more than 24. I don't think it is
outside
the realm of possibility that a candidate expected to place third
would actually place second.
You can't really conclude A voters are misinformed, not from the votes
anyway.
Yes, I only talked about one potential explanation (= A and B voters
misinformed) to why the votes are what they are. There may be also
other explanations, like A voters having no preference between B and C
(B=C), or like the one that A and B were from large established
parties and they wanted to ignore C to make him/her look like
insignificant. I think the given votes should have at least one
rational explanation to prove that the method may give unwanted
results in some real life situations.
A voters are going to win it, and voting A>B turns B into the
CW. Notice that C is not really very close to winning.
Fundamentally, if I said only one thing: I
don't
believe that the margins
ranking of defeat strength (resulting from
its
treatment of unranked
candidates) is in agreement with what voters
would
expect and want.
What would you consider to be a better approach
than
margins for sincere votes? (winning votes has also
scenarios
that may be questioned)
Maybe Range? I guess I don't see that question as
interesting or useful.
Yes, Range could be considered more ideal at least for some
uses (when one wants to maximize the sum of utilities)
(there are also other alternatives like minimizing harm to
some and seeking majority). The problem of course is that it
is so difficult to collect sincere ratings. I think the
question is important since performance with sincere votes
(= elect the correct winner) is important.
It is difficult to collect sincere ratings. But doesn't your question
assume we can get them?
Ok, my question talked only about sincere votes (but I wanted to
assume that both components, performance with sincere votes and
performance with strategic votes, will be considered at some point).
By the way, I do want to maximize the sum of utilities. I just don't
think you can be so direct as to ask for them.
Sum of utilities would be a good approach for many uses if we could
get the personal utilities. In some non-competitive elections and
polls we can get them but political elections may be a more difficult
environment.
(There may also be some extreme situations where the sum of utilities
is not what we want. For example it might make sense to improve the
utility of all voters worth 10 points rather than improve the utility
of all but one voter with 12 points and then kill or otherwise cause a
major decrease in utility to that remaining one voter. In this case
one could btw also consider allowing the voters to give ratings like
"minus infinity" to avoid this kind of situations, i.e. ratings would
not be based on a fixed range but some wider scale, maybe indicating
that 0 means "neutral", 100 means "I like a lot" etc.)
I wonder how the idea of performance given sincere votes applies to WV
and margins for you. If everyone ranks all the candidates, they'd be
the same method. If people are truncating, I do prefer WV for the
reason
I've already said, that WV treatment of truncation is better (closer
to
what is expected) because it places more weight on the "least
abstained"
contests.
I read that so that you like the performance of WV in some strategic
voting scenarios. Maybe you assume that their differences with sincere
votes are not big enough to influence your preferences.
I maybe lean somewhat more in the direction that strategic voting
probably will not be very widely spread in typical large political
elections. In this situation the performance with sincere votes
becomes more important. And the way that margins handles sincere votes
looks to me more natural than the approach of WV. In margins one can
discuss if 45:40 is equal in strength than 15:10 (when there are 100
voters) but it looks more obvious to me that 45:0 should be considered
to be a stronger opinion than 46:45 (WV and margins differ here). I
believe there are practical situations where this difference between
WV and margins may materialize in the results of real life elections
(and where WV results could be considered "strange"). I also tend to
think that in the realm of strategic voting there are also cases where
margins performs better than WV (although these differences may not be
that critical if strategic voting in Condorcet methods is difficult
enough to keep most voters sincere).
You have probably explained before why you think margins is more
intuitive than WV even given *sincere* votes. I don't remember what
the
summary of this is though.
Maybe I already gave some answers to this above. The difference
between 45:0 and 46:45 maybe points out the nucleus of my thinking in
this area. If strategies are not used widely then one should put more
weight on performance with sincere votes.
(Note btw that in another mail I just mentioned
also the
possibility of allowing B and C to formally team
up so that
defeats within their team would not be considered
as severe
as defeats between A and the team.)
This doesn't interest me much (same as Forest's
suggestion of pre-
election agreements in DYN) because I'm not interested
in the case that
a single party (for all practical purposes) nominates
two candidates.
I don't think that will normally happen or be
desirable under any
method. What I'm concerned with is the viability of a
"third" option and
voting for the third option.
I don't believe such strong methods like teaming would be
generally/typically needed. But if there are problems then
teaming may be a good way to overcome them (they may e.g.
quite efficiently cut out any strategy considerations). I
also understand that in some environments all "agreements
between parties" may be considered to represent too much
some "spirit of old times".
In summary, maybe the "third" party explanation is more
what you are after than the "not heard of C" explanation. In
the example "B" and "A" voters were maybe from some old
established parties and they did not want to recognize the
emergence of a "third" new strong candidate.
Yes, that's right.
I believe such
problems may well be temporary. If one adopts a new method
that allows also "third" candidates to run in a meaningful
way and with real chances to win if they have strong enough
support, then I'd guess the attitude and problems of
ignoring them and not ranking them could fade out very soon.
The two main contenders and voters that support them can not
pretend any more that other candidates do not exist (one can
e.g. not play down a candidate with 27% of the first
preference votes).
That would be nice, but even if true, it is just a mitigation of the
problem, not a reason to refrain from eliminating the problem.
Yes, problems should be solved in any case (in the order of severity,
maybe solving some of the least severe problems only partially or
leaving them unsolved since some problems will always remain since no
voting system is perfect in all aspects). In this case it was
difficult to me to say which one was the root cause, the method or the
political set-up and the resulting insincere voting behaviour.
There are also many ways to read the different examples and political
set-ups. For example in the given example the truncation of the B
supporters was in a way punished by margins when A was elected. WV
would make it possible for B supporters to continue truncating their
vote and not indicate their support to C (assuming that B supporters
generally prefer C to A). The support of C could grow within the "BC
wing" to 49:A, 6:B, 45:C>B and B would still win with WV if B
supporters truncate.
Juho
Kevin Venzke
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