[EM] 2. Re: Methods (Markus Schulze)

[Kristofer Munsterhjelm]

On 06/26/2014 05:10 AM, S Sosnick wrote:
> Ballot used with Schulze's single-winner system.
>
> Because the Schulze system determines who wins a one-winner election without
> counting how many 1st choices each candidate received, its ranking ballot can differ
> from the ranking ballot used with various other single-winner systems.  Two
> differences are especially noteworthy.
>
> First, a voter can be allowed to assign the same rank to more than one candidate.  That
> voter's ballot will be ignored when comparing the equally-ranked alternatives but
> counted when comparing one of the equally-ranked alternatives with some other
> alternative.  In contrast, with Instant-Runoff, Coombs, Borda, Bucklin, etc., a ballot
> naming more than one 1st choice is invalid.

It doesn't have to be invalid. Say a ballot lists two candidates as tied 
for first. Then two obvious ways of generalizing the points systems come 
to mind, and they have been discussed on this list quite a bit. First, 
there's ER-Whole: give each candidate the total points score. In 
Plurality, if two candidates were ranked equal first, this would give 
one point to both of them. Second, there's ER-Fractional: share the 
total score between the candidates. In the Plurality example above, each 
candidate would get half a point.

ER-Whole tends to reduce to Approval and ER-Fractional tends to reduce 
to Plurality. However, there are exceptions. Consider ER-Whole Bucklin: 
if you don't know whether to approve both Nader and Gore to win against 
Bush, then putting the candidate you like least of the two in second 
rank may work as a hedge.

> Second, one of the alternatives offered to voters can be "None of the above" or--as in
> every statewide election in Nevada since 1975--"None of these candidates."  If that is
> done and a named candidate wins, then you can infer that the winner is, not only
> preferred to the other named candidates, but also favored enough to be (say) hired.
> Conversely, if "None" wins the election, then you might conclude that none of the
> named candidates should be hired.

It's funny you should mention NOTA and Schulze's method. Debian uses 
Schulze's method and also has a NOTA option. The Debian constitution says:

5.2.5 The options on the ballot will be those candidates who have 
nominated themselves and have not yet withdrawn, plus None Of The Above. 
If None Of The Above wins the election then the election procedure is 
repeated, many times if necessary.

(https://www.debian.org/devel/constitution)

So using Schulze's method does not preclude a NOTA. Nor does it make 
supermajority elections impossible, since Debian also has those.