Thanks, that confirms my understanding. The problem here in he UK is that in many seats we do have 3 big parties, and in Scotland and Wales, where there are nationalist parties included also, there are sometimes 4. (Northern Ireland has even more!) In these cases not voting tactically under AV may have the reverse effect to the voters intention.
Faced with examples of instances where AV can fall prey to voter strategy, the contention of the more thoughtful members of the Yes campaign is that, tactical voting may theoretically be possible under AV, but only in very rare circumstances, or that AV makes it so difficult to vote tactically that in practice no-one will bother. These are difficult claims to counter by example alone. There is a bit of research supporting that view which is quoted in the Wikipedia piece "John J. Bartholdi III, James B. Orlin (1991) "Single transferable vote resists strategic voting,"" I can't say my understanding of it is all that great, but it seems to be based on computer modelling of elections to find out how often tactical voting can make a difference. My questions are, I suppose, how good is this research? Is there other research with computer models that contradicts this result? How well can we quantify the differences?
---- Election-Methods mailing list - see http://electorama.com/em for list info
