[EM] Spoiler Effect on Wikipedia

Eric Gorr eric at ericgorr.net
Thu Nov 11 10:12:33 PST 2004

At 6:04 PM +0000 11/11/04, Paul Crowley wrote:
>On Thu, 11 Nov 2004 12:08:31 -0500, Eric Gorr <eric at ericgorr.net> wrote:
>>  hummm....there appears to be two opposing points of view here.
>>  Chris B. claims that IIA satisfaction does imply ICC satisfaction.
>>  Markus S. claims that it does not.
>I'm responsible for the edits to that page that make that claim, but
>if it's wrong please do fix it.  Markus S - I'm very surprised that
>IIA does not imply ICC, could you give an example?  I mean the strong
>version of IIA, the one that no reasonable system satisfies.

I think you mean the strong version of IIA which no ranked ballot 
method can satisfy.

Unless I am mistaken, Approval Voting does satisfy IIA and I find AV 
to be a reasonable system. :-)

This nuance is missing on the page 
(http://en.wikipedia.org/wiki/Spoiler_effect) as well when it is 

   A voting system which satisfies the independence of irrelevant
   alternatives criterion is immune to the spoiler effect, but Arrow's
   impossibility theorem shows that complete satisfaction of this property
   is incompatible with other desirable properties of an electoral system.

Arrow's impossibility theorem only applies to ranked ballot voting 
methods and AV is not a ranked ballot method.

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