Jameson Quinn wrote:
2011/11/29 robert bristow-johnson <r...@audioimagination.com
<mailto:r...@audioimagination.com>>
IRV, with its kabuki dance of transferred votes, is more complicated
than Condorcet. when i was asked by one of the leaders in this town
of the anti-IRV movement to explain Condorcet simply (since that was
most of their case against IRV - most of their signs said "Keep
Voting Simple"), i answered "If more voters agree that Candidate A
is a better choice for office than Candidate B, then Candidate B is
not elected." pretty simple and hard to argue with.
This is a good description. However, it still conflicts with most
people's mental paradigm for how an election works, and so it seems more
complex than it is. Most people think an election is something like this:
1. People vote.
2. Those votes are translated into a score for each candidate.
3. The best score wins.
Plurality, Borda, Majority Judgment, Approval, and Range all fit that
paradigm. (That's why people are so prone to reinventing Borda.) Even
IRV and SODA can be shoehorned in, though it's a stretch. But Condorcet
depends on a matrix, not a list of scores; and that just doesn't fit
inside people's heads.
If IRV can be stretched to fit that, then surely the Smith-Approval
method we gave to Clinton Mead would also fit. "Rank the candidates in
order of how many voters explicitly ranked them on their ballots. Take
the two candidates closest to losing, and consider them free of the
other candidates' interference: eliminate the one who is preferred to
the other less often than the other is preferred to him. Keep
eliminating until you have a single winner".
If you want to coat it appropriately, you could probably phrase it in
terms of a duel between the losers, a saving chance at being redeemed
from elimination, something like that.
Or Minmax: "Each candidate's score is the number of votes he'd get in
the second round of a runoff against the rival who'd have the strongest
showing against him. The candidate with the greatest score is strongest
even at his weakest, so he should win". That one is a little more
matrix-y, but it still only implicitly mentions it.
I agree absolutely. That's why I think Range is not nearly as good as
Bayesian Regret would lead us to think. So, how much does each system
burden voters with the need to strategize, and how much does it punish
them for not strategizing?
I wonder if that could be simulated. I seem to recall reading a paper
that showed that methods that are monotone can be very easily
manipulated when there exists some sort of strategy that can make one of
exactly two candidates win. That is, it can find such a strategy in
polytime if there is one.
Given such a quick strategy-finding algorithm, one could then let only
one side strategize, and see if that would make the method shift the
winner. Then one could compare the simulated utility for the candidate
that wins under one-sided strategy to the one that wins under no
strategy. Good rules would tend to permit only "relatively good"
candidates to win through strategy, compared to what you'd get under
honesty.
It wouldn't be perfect, of course. The strategy might be very complex to
pull of in practice, and it wouldn't cover the cases where there are
multiple candidates that can be made to win through strategy.
----
Election-Methods mailing list - see http://electorama.com/em for list info
