[EM] Re: reccomendations (Schwartz // SC-WMA correction)

[Chris Benham]

James Green-Armytage wrote:

>Am I correct in observing that Schwartz // SC-WMA is similar to completing
>Condorcet with Schwartz and then Bucklin? How does the former differ from
>the latter?
>
>my best,
>James
>
>
>  
>
CB: Bucklin hopelessly fails Clone Independence, and so (according to 
EMR) is vulnerable to crowding 
<http://condorcet.org/emr/defn.shtml#crowding>  and teaming 
<http://condorcet.org/emr/defn.shtml#teaming>.
I  would never knowingly reccomend a method that does that.
On the other hand Bucklin meets  Mono-raise,  and SC-WMA  (I  think 
fairly benignly) doesn't.

Here is a simple example from Marcus Schulze:
2: A>B>C
3: B>C>A
4: C>A>B

Bucklin and  SC-WMA both elect C.
Now we  replace C with the clone set  C1, C2, C3.

2: A>B>C2>C1>C3
3: B>C3>C2>C1>A
4: C1>C2>C3>A>B

Now Bucklin elects B.

SC-WMA "Weights": A:2,  B:3,  C1: 4,  C2: 0,  C3: 0.
Each ballot approves from the top, until at least half  (by "weight") of 
 the candidates have been approved. Thus:

2:A,B
3:B,C3,C2,C1
4:C1,C2,C3,A

Final "approval" scores: A:6,  B:5,  C1: 7,  C2: 7,  C3: 7.

The three clones are tied for first. I would  favour resolving this by 
electing the tied candidate with the greatest  "weight", C1.

Chris Benham



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