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

Eric Gorr eric at ericgorr.net
Fri Jan 23 11:52:06 PST 2004

At 1:28 PM -0600 1/23/04, Paul Kislanko wrote:
>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

I have made no such assumption.

Pretend that Candidate A is pro-aborition. Candidate N is 
anti-aborition. The voter could easily rank:

   A > B = ... = M > N

If the voter sees no relative difference of candidates B - M, there 
is no need to fully rank them.

Still, all preferences matter.

>assuming that reading the ballots backwards implies a "dislike" function the
>same way that reading it forward implies a "like" function.

This is simply what ranked ballots are. The alternatives are ranked 
by a voter from most to least liked.

>That would only be the case when every voter ranks all candidates, and every
>voter has been told that who they rank last matters.

A full ranking is implied even when the voter truncates. For example,

   A > B > C > D = ... = N

Is the equivalent to:

   A > B > C

and we still have the function you describe.

>No voter I know wants to go to that much trouble.

There is no need to.

>"Which do you like the most" gets to be a harder question after two or three

which is why one allows a voter to rank alternatives as being equivalent.

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