First, Instant Runoff Normalized Ratings (IRNR) explained - in a paragraph: http://bolson.org/voting/methods.html#IRNR slide show: http://bolson.org/voting/IRNR_explaination.pdf (219KB) http://bolson.org/voting/IRNR_explaination.mov (2.3MB)
On Dec 16, 2004, at 5:33 PM, Forest Simmons wrote:
Date: Wed, 15 Dec 2004 20:30:19 -0800 From: Brian Olson <[EMAIL PROTECTED]> Subject: Re: [EM] Is range voting the panacea we need?
Straight rating summation is vulnerable to strategic voting. Perhaps in
this study people voted honestly because it obviously didn't matter and
so there was no incentive to vote strategically. In a real election the
stakes would be higher.
My favorite solution is to run Instant Runoff style disqualification cycles over Normalized Ratings (IRNR). I believe this method is strategy proof and passes a handful of other desirable election method criterion.
In general, methods that proceed by sequential elimination are not strategy proof:
Suppose that there are only three candidates, and you think that your compromise C has a significantly better chance than your favorite F of winning against the candidate D that you dislike the most, and that there is a good chance that D will be one of the finalists. Suppose further, that F and C both have decent chances of getting into the final round.
In this situation, you have an incentive to "bury" your favorite F, i.e. to try and make F lose in the first round.
I don't think this can happen with IRNR.
If I truly prefer F>C>D, if I'm right about IRNR then it should be impossible to find a configuration of votes for which it's better for me to vote C>D>F (or C>F>D ?). In this hypothetical vote configuration, if I vote honestly F>C>D, then D will be elected, but if I vote C first, C will be elected. But this is not possible with IRNR because of the re-normalization process that happens on each round.
If I vote F=1.0, C=0.8, D=0.0 and F is disqualified, then my second round re-normalized vote is C=1.0, D=0.0 . In fact, no matter what my rating of F and C (holding D constant at 0.0), if either of them is eliminated in the first round, my second round vote will be {the remaining of F or C}=1.0, D=0.0 . And if that doesn't elect someone I want, nothing will.
Did I miss something in my steps or misunderstand the challenge?
I remember that the question of strategy came up before, and I think I should reduced my claim. In the zero information case, a single IRNR voter maximizes zir expected utility by voting honestly. With partial information, a voting bloc may be able to improve the outcome for them by artificially deflating the ratings for a close competitor. As usual, with faulty partial information and possibly competing strategic voting blocs, they may wind up shooting themselves in the foot and making way for a third choice.
For this reason Kevin came up with the "Runoff Without Elimination" idea, culminating in his "Gradual Approval," which I believe to be a superior use of Cardinal Ratings style ballots.
It doesn't suffer from the burying strategy because all candidates are still in the race in the last round.
A candidate with lots of success in previous rounds just gets the approval cutoff moved closer to her as a "reward," so losers of previous rounds (whether favorite or compromise or both) still have chances in the final round.
This sounds like an interesting method that I missed. Is there a reference description of it?
Brian Olson http://bolson.org/
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