Kevin Venzke wrote: > > The simplest FBC failure scenario I can think of looks like this: > > 6 A > 2 B > 2 C=B <<< (sincere is C>B) > 3 C>B > > A and B are the lesser evils.
Note: I re-ordered the lines above to more clearly show B as the apparent centrist, between A and B. I didn't alter the contents of the lines. I don't think this is a particularly obscure example. Suppose A is the incumbent, with B and C members of a split challenging party. This scenario seems all too common. The only thing missing are the A-leaning swing voters, who lean B>>A>C. > B is eliminated and A beats C, when the two voters vote C=B. However, this > only happens because the 3 voters buried their support for B. If the lesser > evil candidates are always promoted to (equal) first place, on everyone's > ballots, then I don't see how there would be any FBC failures. > > Reasoning: If lesser evils never have lower preferences, only first preferences, > then A is either going to have more votes than B or he isn't. Eliminating > other candidates isn't going to change that. Right-- if they vote as though it were straight approval voting. I agree. This is why consider approval voting a better system than ER-IRV(whole). > I think for the C=B voters to vote B>C, they would have to believe that C > can't beat A, and that despite this, more voters will vote C>B than B. Well, it's true, isn't it? So all they need is an accurate poll. It's possible that of the two sincere C>B groups, the B=C voters have a weaker preference between the two, and/or a belief that B is better positioned to defeat A. I can't think of another reason to differentiate them from the C>B voters. It might be reasonable to assume that if the B=C voters didn't have the ER option, some would strategically rank B first and some would sincerely rank C first. If half-and-half, ER-IRV is neither better nor worse than plain IRV. On the other hand, the fact that they voted B=C might indicate that they were inclined to vote strategically anyway. It's clear that these two voters would have been better off voting B>C, so maybe they would have voted that way. With approval voting, it might be reasonable to assume that some of the C>B>A voters would have voted C=B (with the remainder bullet voting for C). If two of these voted C=B in the example above, the outcome would have changed. Regardless of the outcome, the existing B=C voters would not have been committing a strategy error under approval voting (hence FBC). > I think the voters risking the election are those who DON'T use approval > strategy. I don't think that's a valid generalization. The statement is true enough for the more extreme voters, who voted C>B, but in this case the voters who DID use approval strategy were the ones who blew the election. Note that the C>B voters were ranking sincerely, while the B=C voters were apparently attempting to use strategy (they just didn't use a strong enough strategy). > --- Bart Ingles <[EMAIL PROTECTED]> a �crit : > > > What would convince me otherwise would be a set of strategy equations > > comparable to those used for calculating optimal strategy in approval > > voting, or possibly simulations with ER-IRV(whole) showing that > > "lesser-evil or better" strategy is as good or better than > > "lesser-evil-only" in terms of social utility efficiency. Another thought-- has anyone calculated the best zero-info strategy under ER-IRV(whole)? Is it to rank sincerely, use approval strategy, or something in-between? > Well, I can't produce these, at least not at the moment... But my thoughts > would be: > > "Lesser-evil-only" will only elect lesser evils. > "Lesser-evil or better" could elect a more broadly appealing candidate, just > as in Approval. The problem is that the C>B>A voters mistakenly believed that ranking B second was enough. This was a kind of a "sucker bet", much like giving a partial rating under Cardinal Ratings. Then again, the C=B>A voters were also commiting a "sucker bet". It's not that they were wrong-- you can be wrong in approval voting too-- it's that they were'nt maximizing their chances. > Again, if people are using "lesser-evil or better" strategy, I don't know > where the FBC failures come in. You did a good job of illustrating one above; I think where we differ is the likelihood of it happening. We haven't touched on nomination strategy, but if the B and C were members of the same party, it would be in the interest of the party to make sure that C was kept off the ballot. Hence the Duverger effect. Bart Ingles ---- Election-methods mailing list - see http://electorama.com/em for list info
