On 28 Nov 2011 20:24:37 -0800, Chris Benham wrote: > > Matt Welland wrote (26 Nov 2011): > > Also, do folks generally see approval as better than or worse than IRV? > > To me Approval seems to solve the spoiler problem without introducing > any unstable weirdness and it is much simpler and cheaper to do than > IRV. > > If we are talking about the classic version of IRV known as the > "Alternative Vote" in the UK and "Optional Preferential Voting" in > Australia, then I see IRV on balance as being better than Approval. > > The version of IRV I'm referring to: > > *Voters strictly rank from the top however many or few candidates > they wish. Until one candidate remains, one-at-a time eliminate > eliminate the candidate that (among remaining candidates) is > highest-ranked on the fewest ballots.* > > The "unstable weirdness" of Approval is in the strategy games among > the rival factions of voters, rather than anything visible in the > method's algorithm. > > Approval is more vulnerable to disinformation campaigns. Suppose > that those with plenty of money and control of the mass media know > from their polling that the likely outcome of an upcoming election > is A 52%, B 48% and they much prefer B. > > In Approval they can sponsor and promote a third candidate C, one > that the A supporters find much worse than B, and then publish false > polls that give C some real chance of winning. If they can > frighten/bluff some of A's supporters into approving B (as well as > A) their strategy can succeed. > > 47: A > 05: AB (sincere is A>B) > 41: B > 07: BC > > Approvals: B53, A52, C7
I find this example contrived. * If mass polling is available, many people will be aware of the 52/48 split between A and B ahead of time. * Corruption is a separate issue. With proper election funding control, support for C would be restricted. > Approval is certainly the "bang for buck" champion, and voters never > have any incentive to vote their sincere favourites below > equal-top. But to me the ballots are insufficiently expressive by > comparison with the strict ranking ballots used by IRV. I agree. Approval-Bucklin (AKA ER-Bucklin) has the advantage in your contrived example of allowing the A > B voters to add B at a lower rank, which would not count unless neither A nor B achieves a majority. In many cases, it would not be necessary to rate candidates at the second (or lower) choice option, but having that option increases the available nuance of the vote. > IRV has some Compromise incentive, but it is vastly less than in > FPP. Supposing we assume that there are 3 candidates and that you > the voter want (maybe for some emotional or long-term reason) to > vote your sincere favourite F top even if you think (or "know") that > F can't win provided you don't thereby pay too high a strategic > penalty, i.e. that the chance is small that by doing that you will > lose some (from your perspective positive) effect you might > otherwise have had on the result. However IRV does impose a false choice -- that you must rank your preferences separately, no equal ranks allowed. > In FPP, to be persuaded to Compromise (i.e.vote for your compromise > "might win" candidate C instead of your sincere favourite F) you > only have to be convinced that F won't be one of the top two > first-preference place getters. > > In IRV if you are convinced of that you have no compelling reason to > compromise because you can expect F to be eliminated and your vote > transferred to C. No, to have a good reason to compromise you must > be convinced that F *will* be one of the top 2 (thanks to your vote) > displacing C, but will nonetheless lose when C would have won if > you'd top-voted C. > > In my opinion IRV is one of the reasonable algorithms to use with > ranked ballots, and the best for those who prefer things like > Later-no-Harm and Invulnerability to Burial to either the Condorcet > or FBC criteria. But are these the criteria we really want to achieve in a single-winner election? To say that LNH is the most important criterion is, at its most basic level, an emotional argument. While effective in persuading the electorate, I think what we really want to look for is a method that does a good job of finding the candidate closest to the center of the electorate, while resisting strategic manipulation. Ted -- araucaria dot araucana at gmail dot com ---- Election-Methods mailing list - see http://electorama.com/em for list info
