Hi,
Some comments below.
On Jul 11, 2008, at 2:42 , Kevin Venzke wrote:
Hi Juho,
A quick response.
--- En date de : Mar 8.7.08, Juho <[EMAIL PROTECTED]> a écrit :
Ok, this is a good concrete example scenario. The votes are
of course
simplified. Surely there would be also considerable number
of other
kind of opinions than these three.
But let's see first where these simplified votes could lead to.
Sincere opinions:
45 A>B>C
40 B>A>C
15 C>B>A
It seems that C is an extremist candidate (at the B side of
the
political map since they prefer B over A). In line with
this
explanation it is natural that A supporters prefer B over
C. It is a
bit more strange that all B voters prefer A over C. Maybe C
is so
radical that all others hate him/her. (The nature of the
scenario
will however stay quite similar even if there were also
some B>C>A
voters.)
The A party or A proponents have a plan to bury B under C.
I don't know about this. Is it necessary to have a plan? This isn't
like
pushover strategy where only a certain percentage of the faction
should
vote in a certain way, or risk failure. You're not going to be the
"one
strategizer too many."
My thinking was that someone has to at least understand that burial
could be attempted in this case and then plan how to communicate the
request to vote strategically to the voters. Well, in principle it
could be that already during the previous elections voters were made
aware of the strategic voting options, but I think it is much more
probable that someone will try to make the decision that according to
the polls candidate A is now in such a position that burial could be
attempted. This then has to be communicated (by active media or A
promoters) to the potential supporters of candidate A. If there is no
plan and clear communication then the outcome could be that some of
the A and B supporters would bury and some not (i.e. voters are not
knowledgeable strategists that could make these decisions by
themselves).
What if the A proponents manage to get the required 89%
strategic
votes or more to support their strategic plan? Then the C
supporters
can use a compromise counter strategy and rank B first. If
more than
5 of the C supporters will use this strategy that will
nullify the A
strategy even if they manage to get 100% of the A
supporters to
follow the strategy. Less strategic C voters needed if less
than 100%
of the A voters will follow the strategy.
Nullification is no consolation though, because there is nothing to
fear
from it. You may as well say that some of the C voters strategically
vote for their last choice A in order to make A a majority favorite so
that A voters' strategy does nothing.
Theoretically there could be a society where all voters would vote
strategically even if they would not benefit anything out of it. In
most societies strategic plots have however also some negative
effects (like losing some of the crucial voters with sincere
utilities A=100, B=99, C=0). Most societies also contain voters that
will not try to fool the system since they consider that to be foul
play. There is of course also always the risk of electing candidate
C. The strategists must thus do careful analysis on the chances of C
before recommending strategic voting (not a free ride in that sense).
General burial is not a very good strategy (e.g. 40 A>X1>...>Xn>B, 40
B>X1>...>Xn>A, 10 ...).
The point thus is that even if there are some voters that might be
eager to follow whatever strategic options no matter what the outcome
is there also also many other kind of voters. Also nullification may
be a reason not to vote strategically to many. Also within the
election method discussion community some people have indicated that
they to vote sincerely (e.g. in the US presidential elections) even
if that is not optimal from a short term strategic point of view.
If the method uses winning votes then the B supporters may
also use
truncation as their counter strategy. 30 votes or more (out
of the
40) needed. That would be a threat to elect C if A voters
will apply
the strategy.
Yes. If WV or Condorcet//Approval is used I don't believe there
would be
a problem, since truncating the worse frontrunner would be both
natural
and effective. (Actually, as long as truncation is allowed I believe
voters won't rank the worse frontrunner anyway, even if you tell
them they
ought to or safely can.)
Unfortunately there might be other problems. The same set of votes
that demonstrates how truncation works as a defence strategy (45
A>C>B, 40 B, 15 C>B>A) serves as an example of a case where use of
winning votes makes it possible for the C supporters to strategically
bury A under B (sincere votes: 15 C>A>B).
Also the behaviour of winning votes with sincere votes can be
questioned, as well as the idea of favouring truncation (brings the
elections closer to plurality).
I try to study the possibility that Condorcet methods are
sufficiently strategy proof for large public elections (with
independent decision making) as such. If they lead to strategic
voting and counter strategies that may already be a sufficient reason
to use some other safer and simpler methods. I'd maybe expect all the
main parties to generally recommend sincere voting to consider
Condorcet to be a good method for that society (i.e. Condorcet should
be safe enough to allow them to comfortably fall on that side of the
fence). (What do you think of this statement as a criterion on
whether Condorcet will work well in the society in question or not?)
I'll skip detailed analysis of Condorcet//Approval. There are some
problems with either not allowing all candidates to be evaluated
(with implicit cutoff) or being more complex to the voters (with
explicit cutoff).
Theoretical examples on paper give complete information of
the
opinions and allow complete control of (uniform) voter
behaviour, and
My claim is that the former is plausible (at least the information
will be
complete to the extent necessary) and the latter unnecessary, when
it's predictable that truncation will not be used.
On the first topic I'd expect something like 5% changes in the
support of the major candidates to be possible before the election
day. In some situations this may be enough, in some not. Cases where
that accuracy is enough may be more difficult from strategy
implementation point of view.
For this reason I recommend using concrete examples from real life
with explicit votes when studying the vulnerability of different
methods (i.e. general claims that rely on all details to work out the
best/worst way simultaneously are not reliable).
On the second topic I expect most strategies to require some sort of
central control/guidance to make them work. And I expect the voters
to be a heterogeneous group that typically to some extent also
objects to strategic voting and to being controlled / told how to
behave by others. Also people with preferences of different strength
are likely to behave in different ways. These are only some reasons
why people tend to build their own logic and make their own decisions.
I guess you don't think that voters should generally bury or apply
their own knowledge to decide whether to bury or not (i.e. some
control/guidance needed in public elections to make the behaviour of
the voters with strategic interests uniform and to make the
strategies work even partially). If so, then the voters need to rely
on some external source that tells them that they should bury B under
C. Also strategy related articles in the media might be inaccurate
and conflicting (e.g. if you would let the EM people write them :-).
(One more reason why A voters should not use burial
strategy is that
if C is stronger than expected then their strategy might
also lead to
electing C instead of B.
If there's any possibility of this scenario, I don't believe people
would
use burial.
In the given example that line would go at about where the opinion
division among B supporters is 10 B>A>C, 30 B>C>A. Some B supporters
surely prefer C over A. The strategic plot of A supporters might move
some more B supporters to that camp. If candidate A loses some
supporters because of the plot or for any other reasons that also
increases the chances of C to win. Also C may gain more votes and
thereby increase the risk. One must thus count some tolerances based
on the uncertainty of the polls, and possible changes in opinions,
and reactions to the plot when estimating the viability of the strategy.
If we would modify the example in such a direction that the strategy
could be successful without requiring 89% of the A supporters to
implement the strategy that would probably also increase the risks.
There is thus a balance between working vs. non working strategy and
risks vs. no risks.
My request was to identify such real life scenarios where the risks
would be small enough and the probability of success would be high
enough. I don't think the given scenario would still be a major
threat in most societies. Are there others that would be more likely
to succeed? Or alternatively, are there some general rules that could
be used by the Condorcet voters to decide when it is strategically
better to bury than not to bury?
Juho
Kevin Venzke
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