Dear Chris Benham, you wrote (15 June 2004): > According to Mike, it meets his "Weak Defensive Strategy > Criterion" (WDSC): If a majority prefers one particular > candidate to another, then they should have a way of > voting that will ensure that the other cannot win, > without any member of that majority reversing a > preference for one candidate over another.
You wrote (16 June 2004): > Thanks for your interest and good example. Maybe somewhat > confusingly, Steve Eppley gives two versions of this > criterion (same name and author, but slightly different > definitions). > > Here is the other one: > > non-drastic defense: If more than half of the voters > > prefer alternative y over alternative x, then that > > majority must have some way of voting that ensures x > > will not be elected and does not require any of them > > to rank y over any more-preferred alternatives. (This > > is promoted by Mike Ossipoff under the name Weak > > Defensive Strategy Criterion. Non-satisfaction means > > some members of the majority may need to misrepresent > > their preferences by voting a compromise alternative > > over favored alternatives if they want to ensure the > > defeat of less-preferred alternatives.) > > In your example, y is A and x is E. The top three groups > of voters, who all ranked A equal first with two other > candidates, can ensure that E is not elected by ranking A > alone in first place. There is no candidate that they > prefer to A, so ER-IRV(fractional) seems to meet this > version (as Mike Ossipoff in effect claimed). What do you think about this example?: 10 B>C>A>E>... 10 B>D>A>E>... 10 C>B>A>E>... 10 C>D>A>E>... 10 D>B>A>E>... 10 D>C>A>E>... 7 B>E>... 7 C>E>... 7 D>E>... 38 E>... A majority of the voters strictly prefers candidate A to candidate E. In my opinion, this example demonstrates that ER-IRV(fractional) violates Mike Ossipoff's WDSC and Steve Eppley's "non-drastic defense" criterion. What do you think? Markus Schulze ---- Election-methods mailing list - see http://electorama.com/em for list info
