At 04:31 AM 12/21/2008, Kristofer Munsterhjelm wrote:
In any case, it may be possible to have one of the LNHs and be monotonic and have mutual majority. I'm not sure, but perhaps (doesn't one of DAC or DSC do this?). If so, it would be possible to see (at least) whether people strategize in the direction of early truncation by looking at methods that fail LNHarm but pass LNHelp; that is, Bucklin. Was bullet voting pervasive under Bucklin?
In some contexts, yes. However, we see upwards of 30% or so usage of additional preferences in the municipal elections I've looked at. I consider that high. Bullet voting occurs for reasons other than LNH concern. As Lewis Carroll pointed out, it's simply how many people will vote, representing their best knowledge, they may not have sufficient knowledge to intelligently rank or rate the rest of the candidates. Further, if they have strong preference for their favorite over all others, they may not care to vote for any of the others, not wanting to contribute to the victory of any of them. Voting is a moral action, and choosing the lesser of two evils isn't always the best thing to do. Sometimes the best action is to reject both evils, and that's what a bullet vote for the best candidate could be doing.
In other words, Nader supporters in 2000, if they really believed that Gore and Bush were Tweedledum and Tweedledee, might not have added an additional ranked choice for Gore even if the method had allowed it, and LNH has nothing to do with that.
We don't know, unless we do some serious ballot analysis -- the necessary information is available from a few elections now -- how many IRV voters truncate, because we don't know the lower preference expressions from those who did vote for a frontrunner. My guess is that the numbers are quite similar to what I've seen with Bucklin historically and what I'd expect from Bucklin today.
We can stil get some idea of how easily voters would strategize by looking at Bucklin, though; or for that matter, at ranked voting methods that fail both LNHs. Schulze's used in some technical associations (Debian, Wikimedia), and, although I don't have raw voting data, they seem to be mostly honest. The Wikimedia election had no Condorcet cycles down to the sixth place, for instance.
What I've seen from Bucklin, there is a very extensive analysis of the Cleveland election of 1915, I think it was, is that voters who didn't want to vote for a candidate didn't. Truncation, at least in Bucklin, is not insincere! All things considered, the numbers of additional preference votes are actually higher than I'd have expected. FairVote claims additional preference votes on the order of 11% in a series of Alabama party primary elections, and that majority failure was universal. I'm not sure what to make of that, beyond a possibility that most primary voters simply knew who their favorite was and trusted that the plurality favorite would be good enough. In nonpartisan elections, it seems, regardless of theory, the first preference leader wins the election, exceptions have to be pretty rare. (None so far in the U.S. with well over thirty such elections.)
11% additional preference will flip some elections, and apparently it did. Indeed, some of the opposition to Bucklin seems to have come from parties and candidates who lost elections due to additional preference votes, considering that this somehow violated their basic right to win if they get the most first preference votes.
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