[EM] No evidence that IRV doesn't fail. Reasons why it must.

[Paul Kislanko]

Eric wrote:

>Consider the case of a polarizing issue, such as Abortion. To
>those on either side, their last place vote will matter just as
>much as their first place vote. Even their middle preferences
>will matter greatly as it puts a buffer between the viewpoint
>they agree with and the viewpoint the simply hate.

There are a lot of implicit assumptions here about which voting method is
being used. You are assuming that fully ranked ballots are being used and
assuming that reading the ballots backwards implies a "dislike" function the
same way that reading it forward implies a "like" function.

That would only be the case when every voter ranks all candidates, and every
voter has been told that who they rank last matters. No voter I know wants
to go to that much trouble. If it is impossible to determine group
PREFERENCES from any voting method, it is certainly impossible to infer
group anti-preferences from one, and to suggest that one can infer both
preferences and anti-preferences is a little extreme.

"Which do you like the most" gets to be a harder question after two or three
spots. "Which do you DISlike the most" is asking too much - once I decide I
dislike an alternative, I don't waste time ranking how much I dislike them
individually. Even in the polarizing Abortion question, were I a "right to
life"-er and abortion were the ONLY thing my little brain could think about,
I would have a hard time deciding which of the "pro-choice" alternatives
seems most disgusting.

The fact that "last place vote matters" is an assumption about the method
being used to count votes. I would suggest rather strongly that any method
that assigns a positive score to a candidate ranked last on a ballot is
fatally flawed.