IRV's nonmonotonicity

[Adam Tarr]

Rob wrote:

>  9:A>B>C
>  8:B>C>A
>  6:C>A>B
>
>A wins by all four methods.  Now four of the B>C>A voters switch to C>A>B, 
>which is "upranking" A by Adam's definition:
>
>  9:A>B>C
>  4:B>C>A
>10:C>A>B 
 >
                                                                             
                                Now C wins.
 

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Donald, who apparently became a IRV fanatic, wrote in part-

Anti-IRV and Anti-STV people need bogus examples to support their bogus
claims that true reform methods are somehow defective.  Rob shows that he
is aware of this when he included in his letter the following: "(why would
every B voter rank C second, but no C voters rank B second)"
----
D- Some folks continue to remain clueless about ALL methods having problems 
with 3 or more choices if there is no first choice majority.

Once again --

Times are rough and tough -- such as 1932.  Extremists seem to be vogue. 
Moderates seem to be split.

34 HWS
33 SWH
16 WHS
16 WSH

99

With IRV W loses, H beats S 50-49

Who might have a YES majority ???   Could it be W ??

Who definitely beats each of the other 2 choices head to head ???    W.

H Hitler clone, S Stalin clone, W Washington clone

I suggest that ANY method that uses ONLY PART of the data in the method is 
severely defective.

IRV uses ONLY part of a place votes table when it eliminates candidates and is
 thus severely defective.

Thus -- voting YES or NO on each choice obviously uses ALL of the data.

Thus -- Number Voting (1, 2, etc.) using Condorcet (head to head) uses ALL of 
the data.

How many methods use ALL of the data in the method ???

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Alex wrote in part-

It is not unreasonable to assume this profile:


30% Bill > George > Ross

 7% Bill > Ross > George

25% Ross > George > Bill

 6% Ross > Bill > George

25% George > Bill > Ross

 7% George > Ross > Bill


The runoff is between Slick Bill and Papa George.  25% of the electorate

defects to Papa George, and Papa George wins.  Note that Papa George is in

fact the Condorcet winner, and Crazy Ross is the Condorcet loser.


Now, suppose that 2% of the electorate, all from the Bill>George>Ross camp,

votes strategically and lists Ross>Bill>George.  Slick Bill now has 35%

first place votes, Crazy Ross has 33% first place votes, and Papa George

has 32% first place votes.  The runoff is Crazy Ross vs. Slick Bill, and

Slick Bill wins.
---
D- Who, if anybody, has a YES majority in either example ???

I note in the first example  there is (for first place votes only) --

37 % Bill
31 % Ross
32 % George

That is  -- George > Ross by 1 %. (first place votes only).

The general point is that strategy games can happen near *boundaries* with 3 
or more choices.