[EM] Juho--Margins fails Plurality. WV passes.

Juho juho4880 at yahoo.co.uk
Tue Mar 6 13:44:13 PST 2007

The definition of plurality criterion is a bit confusing. (I don't  
claim that the name and content and intention are very natural  
either :-).)
- http://wiki.electorama.com/wiki/Plurality_criterion talks about  
candidates "given any preference"
- Chris refers to "above-bottom preference votes" below

There seems to be (potentially) some sort of an (approval style)  
cutoff 1) before the non-listed candidates of each ballot, or 2)  
before the least preferred candidates of each voter.

Let's assume the following slightly modified ballots.
11: A>B
07: B
12: C>A=B

If there are three candidates, A, B and C, then the "disapproved"  
candidates are
- {C}, {A,C} and {} (respectively) with rule 1
- {C}, {A,C} and {A,B} with rule 2

(Note also that existence of a fourth candidate "D" may have an  
impact on which candidates are considered "disapproved".)

If the voter given "approval" to the listed candidates is intentional  
then rule 1 seems to be the intended interpretation. Otherwise  
interpretation 2 might be correct. Since the cutoff is not explicitly  
mentioned, maybe interpretation 2 makes more sense. In this case the  
Electowiki definition could read: "If the number of voters ranking A  
as the first preference is greater than the number of voters ranking  
another candidate B higher than last preference, then B must not be  


On Mar 5, 2007, at 19:49 , Chris Benham wrote:

> Michael Ossipoff wrote:
>> In a posting to a different mailing list, Markus pointed out that  
>> margins fails the Plurality Criterion, and that wv Condorcet  
>> passes the Plurality Criterion.
> Yes.
> 11: A>B
> 07: B
> 12: C
> A Woodall example that applies. Margins elects A, yet C has more  
> top preference votes than A has
> above-bottom preference votes.
> Chris Benham

All new Yahoo! Mail "The new Interface is stunning in its simplicity and ease of use." - PC Magazine 

More information about the Election-Methods mailing list