Michael Ossipoff writes ("Norman Petry and I (Ossipoff) recommended CSSD, but
Schwartz Woodall is a better voting system for Debian"):
> Example 1:
>
> Sincere preferences:
>
> 99: A>B>>C
> 2: B>A>>C
> 100: C>>(A=B)
>
> The A voters rank sincerely, and the B voters defect:
>
> 99: A>B
> 2: B
> 3: C
In Debian's system, this will result in A winning.
A vs B:
99x "A>B" count as preferring A to B
2x "B" count as preferring B to A
3x "C" count as preferring neither A to B, nor B to A
So A defeats B.
A vs C:
99x "A>B" count as preferring A to C
2x "B" count as preferring neither A to C, nor C to A
3x "C" count as preferring C to A
So A defeats C.
The Schwartz set contains only A.
> 2 defecting B voters have stolen the election from 99 co-operative A voters.
So you have misunderstood Debian's voting system. See particular
Constitution A.6(1).
> ----------------------------
>
> Here's another example in which the 3 factions are nearly equal in size:
>
> Sincere preferences:
>
> 33: A>B>>C
> 32: B>A>>C
> 34: C>>(A=B)
>
> Actual votes, when A voters co-operate and B voters defect:
>
> 33: A>B
> 32: B
> 34: C
A vs B:
33x "A>B" count as A>B
32x "B" count as B>A
34x "C" count neither way
A defeats B by 33:32
A vs C:
33x "A>B" count as A>C
32x "B" count neither way
34x "C" count as C>A
C defeats A by 34:33
B vs C:
33x "A>B" count as B>C
32x "B" count as B>C
34x "C" count as C>B
B defeats C by 65:34
The Schwarz set contains A,B,C. We drop the weakest defeat, which is
A>B by one vote because 33<34.
> Again, though A is CW, B wins by defection.
However this seems quite a risky strategy by the B voters. The
situation seems contrived and unlikely to arise in practice.
Ian.
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