[EM] A completely idiotic Instant Runoff Voting (IRV) election

[C.Benham]

Warren Smith posted (24 Aug 2010)  a link to page discussing a simple IRV
election:

18: A>B>C
24: B>C>A
15: C>A>B

Quoting from the page:

FAILURE OF THE SNIFF TEST: First of all, without any analysis at all, 
who do you think ought to win this election?
It sure looks to me like B is the "most correct" and "most democratic" 
winner. But IRV elects A.



That verdict might be justified on positional grounds: B has both the 
most first preferences and the most

second preferences and so looks the prettier winner.

But the objection is mostly based on ranking information which the IRV 
voters were content to give because IRV meets
Later-no-Harm.  If  the  A and B supporters are mostly concerned to 
elect their favourites ( perhaps encouraged
by accurate pre-election first-preference polling) then with a method 
that fails Later-no-Harm and meets Later-no-Help
(such as Bucklin or  Range / Score) the cast ballots would more likely 
look like:


18: A
24: B
15: C>A

Does A now look like the wrong winner?

Score voting  considers this 
election an easy call. It would elect B if all voters gave score X to 
their first choice, Y to their second,

and Z to their third, for /any/ X?Y?Z, not all equal.



Really?

18: A9,  B1,  C0
24: B9,  C1,  A0
15: C9,  A8,  B0

A wins. Doesn't this example qualify?


Chris Benham













http://rangevoting.org/CompleteIdioticIRV.html





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Re: [EM] A completely idiotic Instant Runoff Voting (IRV) election

[Kristofer Munsterhjelm]

C.Benham wrote:

Score voting  considers this 
election an easy call. It would elect B if all voters gave score X to 
their first choice, Y to their second,

and Z to their third, for /any/ X≥Y≥Z, not all equal.


Really?

18: A9,  B1,  C0
24: B9,  C1,  A0
15: C9,  A8,  B0

A wins. Doesn't this example qualify?


I don't think so. For the first two ballot groups, you have X = 9, Y = 
1, Z = 0, but then you change them to X = 9, Y = 8, Z = 0 for the last.


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[EM] A completely idiotic Instant Runoff Voting (IRV) election

[C.Benham]

C.Benham wrote:

/ Score voting  considers this 
/>>/ election an easy call. It would elect B if all voters gave score X to 
/>>/ their first choice, Y to their second,

/>>/ and Z to their third, for /any/ X?Y?Z, not all equal.
/>/ 
/>/ Really?
/>/ 
/>/ 18: A9,  B1,  C0

/>/ 24: B9,  C1,  A0
/>/ 15: C9,  A8,  B0
/>/ 
/>/ A wins. Doesn't this example qualify?



/
Kristofer M. wrote:

I don't think so. For the first two ballot groups, you have X = 9, Y = 
1, Z = 0, but then you change them to X = 9, Y = 8, Z = 0 for the last.
 



So what does the phrase  "not all equal" refer to then?

Chris Benham



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Re: [EM] A completely idiotic Instant Runoff Voting (IRV) election

[Kristofer Munsterhjelm]

C.Benham wrote:


Kristofer M. wrote:

I don't think so. For the first two ballot groups, you have X = 9, Y = 
1, Z = 0, but then you change them to X = 9, Y = 8, Z = 0 for the last.
  


So what does the phrase  "not all equal" refer to then?


It means that you can't assign the same value to all the variables -- if 
you were to do so, the result would always be a tie.


In other words, it is the constraint that at least one of the following 
must be true:


X != Y
X != Z
Y != Z

where != is the not-equals operator.

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