On Sat, Nov 13, 2010 at 9:46 PM, Dave Ketchum <[email protected]> wrote: > Actually, "differs from plurality" is not a sure indication of failure for > ranked voting - either IRV or Condorcet. > > For Plurality, voter can name only ONE candidate.
David, Not sure why you are restating the obvious. You also are mischaracterizing what I said. Let me try again so you can hopefully get my meaning: I said that for the first time that IRV/STV in San Francisco found a different winner from the winner who would have won using plurality methods (only counting voters' first choices). In other words the IRV/STV winner has been the voters' 1st choice winner until now, so that the extra costs of using IRV/STV produced essentially nothing until this election. My statement has nothing to do with other means of counting rank choice ballots such as Condorcet. SF does not use Condorcet. > > For ranking, voter can vote for more than one, perhaps ranking most desired > over more gettable. > Condorcet will use all that is in the ballot. > IRV will discard some, use the top of what is left, and never see the > bottom of what is left. Not sure that anyone on this list doesn't already know that, so not sure why you're restating the obvious Dave. > > So, three different methods each seeing parts of the voter's ballot. My You just mentioned two methods of counting rank choice votes, not three. > guess is that the top of the IRV ballot is what the voter is presumed to > have chosen in Plurality. What I said is copied below in case you're wondering what I said. Warren Smith has proven that IRV has a very high probability of producing vagaries in cases when it does not produce the same results as a plurality election would. Most often, as we've seen, IRV/STV produce the same results as a plurality election in practice, as was clear if you read the news articles on this SF election. When IRV/STV does not replicate plurality results, it has a high probability of producing results that are nonmonotonic or eliminate the voters' favorite candidate (Condorcet winner). I hope that clarifies for you. I apologize failing to include enough information for you to understand what I said. Perhaps you had not read the two news articles on the election like I had, nor read Warren Smith's prior article that shows how this latest election dodged a bullet. Again, there will not be very many cases like this when IRV fails to elect the plurality winner and actually elects the Condorcet winner. I suggest you read Warren's article on that issue. Kathy >>> - I decoded the ballot images few days ago since there was some >>> interest on the rangevoting list => >>> http://groups.yahoo.com/group/RangeVoting/message/14474 >>> >>> - Warren Smith wrote down some notes on the results => >>> http://groups.yahoo.com/group/RangeVoting/message/14483 >> >> Looks like IRV lucked out and dodged a bullet for a change when it >> differed from plurality for the first time in San Francisco and got it >> right. As Warren Smith points out, if a little over 3,100 more voters >> had ranked Kaplan 1st and Quan 2nd, Perata dead last, then Perata >> would have won instead. We won't have to wait long until IRV gets >> it wrong when it differs from plurality voting, according to the odds >> Warren calculates. >> >> http://rangevoting.org/Oakland2010Mayor.html >> >> explains. Juho's data processing appears to be correct. >> Quan was the Condorcet and IRV winner. >> Perata was the plain plruality winner. >> >> PARADOX: >> If 3135 extra Kaplan>Quan>...>Perata votes are >> added, all ranking Perata dead last and Quan 2nd, that >> causes Perata to (then) win. >> >> It is fortunate for them that those Perata-hating voters stayed home! >> >> -------- >> IRV is is hardly worth all the extra costs and complexity and lack of >> auditability when the chance is so high of not getting a good outcome >> like this whenever the result differs from plurality. >> >> Kathy Dopp > > > -- Kathy Dopp http://electionmathematics.org Town of Colonie, NY 12304 "One of the best ways to keep any conversation civil is to support the discussion with true facts." Fundamentals of Verifiable Elections http://kathydopp.com/wordpress/?p=174 Realities Mar Instant Runoff Voting http://electionmathematics.org/ucvAnalysis/US/RCV-IRV/InstantRunoffVotingFlaws.pdf View some of my research on my SSRN Author page: http://ssrn.com/author=1451051 ---- Election-Methods mailing list - see http://electorama.com/em for list info
