Hi Bob,
--- En date de : Jeu 24.2.11, Bob Crossley <[email protected]> a
écrit :
The problem here in he UK is that in many seats we
do have 3 big parties, and in Scotland and Wales, where there are nationalist
parties included also, there are sometimes 4. (Northern Ireland has even
more!) In these cases not voting tactically under AV may have the reverse
effect
to the voters intention.
Faced with examples of instances where AV can fall
prey to voter strategy, the contention of the more thoughtful members of
the Yes campaign is that, tactical voting may theoretically be possible under
AV, but only in very rare circumstances, or that AV makes it so difficult
to vote tactically that in practice no-one will bother. These are difficult
claims to counter by example alone.
There is a bit of research supporting that
view which is quoted in the Wikipedia piece "John J. Bartholdi III, James B.
Orlin (1991) "Single transferable vote resists strategic
voting,"" I can't say my understanding of it
is all that great, but it seems to be based on computer modelling of elections
to find out how often tactical voting can make a difference. My questions are,
I
suppose, how good is this research? Is there other research with computer
models
that contradicts this result? How well can we quantify the
differences?
I don't think IRV opponents will criticize that IRV is vulnerable to strategic
voting. It's more likely that they will suggest that the characteristics that
make IRV resistant to strategy, also can make its results displeasing even when
no one uses strategy. I believe James Green-Armytage's recent models suggest
that this can produce a nomination disincentive. (Compare FPP's treatment of
multiple candidates: If people don't trust the method to give a fair and
sensible outcome, the voters or nominating forces can reduce the number of
candidates to confuse the method less.)
Or else IRV opponents can criticize non-monotonicity or other things. But, I
don't usually see people argue that non-monotonicity will be exploited by
strategic voters.
Kevin
----
Election-Methods mailing list - see http://electorama.com/em for list info
