Hi folks, For the past four years, I've administered a discussion forum for election methods, and have generally been an advocate for Condorcet voting, which is a form of pairwise voting. It recently came to my attention that the Debian Project uses pairwise voting for electing officers and voting on ballot initiatives. This is *very* cool, and I hope that everyone feels like it's been successful.
I forwarded information about the Debian Project Constitution on to the election-methods-list mailing list, and received the attached analysis from Mike Ossipoff, who was the person who originally educated me on the merits of pairwise voting over other methods, and is very good at pointing out the flaws of any given method. His analysis is below. Using (er, abusing) a Linux metaphor, there's a couple of security holes in your constitution that needs patches. I'm probably not the best person to draft a replacement, since I've been out of touch with my own mailing list for quite some time. The "state of the art" in 1996 when I was engaged in the discussion was "Smith//Condorcet", though I understand that there's since been methods proposed that have even better properties. If "Smith//Condorcet" is good enough, then I'd be happy to draft the language (it's the best method that I understand well enough to write up) :) Anyway, if you are interested in investigating further, you can look at the following resources: Condorcet method homepage: http://www.eskimo.com/~robla/politics/condorcet.html (Perl script and online web app demos available) Election Methods List: http://www.eskimo.com/~robla/em Hope this helps. If you have any questions, I'd be glad to help. Rob Lanphier [EMAIL PROTECTED] http://www.eskimo.com/~robla ---------- Forwarded message ---------- Date: Fri, 04 Feb 2000 03:51:43 GMT From: MIKE OSSIPOFF <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: Debian pairwise voting Hi-- If the Debian rules are strictly followed, then, by rule 3, all options that are dominated [pairwise beaten] by at least one other option are discarded, and references to them in the ballot papers will be ignored. That means that unless there's an "undominated" alternative ("option"), every alternative will be discarded and deleted from the ballots. Rule 4 provides for electing the alternative that dominates all others, if there is one, and rule 5 says what to do if there is more than 1 option remaining--but there will never be more than zero options remaining unless there'd been a BeatsAll winner, a candidate who "dominates" every other candidate. So the rules need work. Rule 3 should be dropped. Rule 5 should just start with "If there is no undominated option, then..." *** With pairwise voting, it makes all the difference how circular ties are dealt with. When Instant Runoff (they call it 1-winner STV) is used to solve circular ties, that means that the group of voters who are in a position to make a circular tie, by order-reversal, or by truncation, sincere or strategic, are also the group that has an automatic win if they do make a circular tie and the middle candidate gets eliminated. Example: 40: A (the A voters truncate) 25: B (2nd choices of B voters aren't listed, since they're likely to be divided both ways, and we don't know which side would get more from them) 35: CB *** The A truncation makes a circular tie, though B is the Condorcet winner. In the resulting IRV count, B gets eliminated, and A wins. The reason why the A voters are in a position to make a circular tie is because A beats B pairwise. Otherwise truncation or order reversal would merely make C win. Since A beats B pairwise, that means that A beats B in IRV after B is eliminated. So pairwise, with circular ties solved by IRV is perfectly set up to reward truncation & order-reversal, and to force a majority to use defensive strategy to get its way. The majority preferring B to A can only prevail if, when A voters truncate, the C voters insincerely move B up to 1st place, with C. If A voters order-reverse, the only way to keep A from winning is if the C voters actually vote B over C, moving B to 1st place, and moving C down to 2nd place. Of course the B voters could also thwart the truncation or order-reversal, if they insincerely vote C over A. But, for one thing, that requires that they know froml which side the truncation or order-reversal will come. I've just described the general pairwise defensive strategy. With most pairwise methods, that's all that's available. With Condorcet's method truncation isn't a problem, and order-reversal can be thwarted by mere defensive truncation by B voters. *** Mike Ossipoff [EMAIL PROTECTED] ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com
