[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Request for comments [voting amendment]

On Wed, Nov 13, 2002 at 06:13:14PM -0500, Buddha Buck wrote:
> Definition:  A "ballot" consists of a ranking A>B>C>D>... of options 
> submitted by a voter.  It defines a total ordering of options for a 
> particular voter (i.e., for any pair of options A and B, we can claim 
> that a particular voter feels either A>B, A<B, or A=B, and iff A>B, then 
> B<A).


Note that A=B only happens for the case where the voter mentioned neither
A nor B in their ballot.  In my opinion, we should ignore the number A=B:
it should have no bearing on the result.

> Let |A>B| be the number of voters who voted A>B.
> Similarly, for |A<B| and |A=B|.
> (Obviously, |A>B| + |A=B| + |A<B| = total number of voters, because of 
> the definition of a ballot.)


> >    2. Options which do not defeat the default option are eliminated.
> >
> >       Definition: Option A defeats option B if more voters prefer optio
> >       A over option B than prefer option B over option A.
> Let A>>B ("A defeats B")        if |A>B| > |B>A|
> Let A==B ("A ties B")           if |A>B| = |B>A|
> Let A<<B ("A is defeated by B") if |A>B| < |B>A|
> (Note: A==A, for all options A)
> Eliminate all options A if Default>>A.
> Clarification:  What if Default==A?

Then A does not defeat the default option.

> >    3. If an option has a quorum requirement, that option must defeat
> >       the default option by the number of votes specified in the quorum
> >       requirement or the option is eliminated.
> Does is mean:
> Eliminate A if |A>Default| < Quorum
> or
> Eliminate A if |A>Default| - |Default>A| < Quorum

It means "Eliminate A if |A>Default| - |Default>A| < Quorum".  You
should have been able to determine this the text I proposed by
examining the definition of "defeat".

> Again, how do we deal with that |A=Default| case?

See above.

> >
> >    4. If an option has a supermajority requirement, that option must
> >       defeat the default option by the ratio of votes specified in the
> >       quorum requirement or the option is eliminated.
> (?) Eliminate A if |A>Default| / |A<Default| < Supermajority Ratio

Yes.  The original language in the constitution makes that clear, I'll
include some of that language in my next draft.

> Again, what about the |A=Default| votes?
> >
> >    5. If one remaining option defeats any other remaining options,
> >       that option wins.
> s/any/all/

Oops, yes.

> "Condorcet Winner"
> If there is a remaining option A, such that for all remaining options B, 
> either A=B, or A>>B.

A=B is a tie -- ties are recognized in a seperate procedural step.

I suppose I could add some rules to recognize ties in additional
places, but in my opinion that's unnecessary complexity.

> >    6. If more than one option remains after the above steps, we use
> >       Cloneproof Schultz Sequential Dropping to eliminate any cyclic
> >       ambiguities and then pick the winner.  These represent a procedure
> >       and must be carried out in the specified order:
> >
> >       i. All options not in the Schultz set are eliminated.
> >
> >          Definition: An option C is in the Schultz set if there is no
> >          other option D such that C is in the beat path of D AND D is
> >          not in the beat path of C.
> Let A>>>B mean there is a possibly empty sequence C, D, ..., E, F of 
> remaining options such that A>>C, C>>D, ..., E>>F, F>>B
> Then B is on the beat path of A.
> The Schultz Set = { A | A>>>A }

No, because the schultz set includes ties.

> Note:  Because A==A, it isn't the case that A>>A, so if the Schultz set 
> includes A, then there must be a B!=A such that A>>B>>...>>A.  Since 
> A>>B, we then have B>>...>>A>>B, so B is also in the Schultz set. 
> Therefore, the Schultz Set can't be a Singleton Set.

I don't agree with this reasoning.  However, once we have a singleton set
we have a winner, so we could almost treat your conclusion as true.

> >          Definition: An option F is in the beat path of option G if
> >          option G defeats option F or if there is some other option
> >          H where option H is in the beat path of G AND option F is in
> >          the beat path of H.
> >
> >       ii. Unless this would eliminate all options in the Schultz set,
> >	   the options which have the weakest defeat are eliminated.
> >
> >	   Definition: The strength of a defeat is represented by two
> >	   numbers: the number of votes for the defeated option and the
> >	   number of votes for the defeating option.
> >
> >	   The more votes in favor of a defeated option, the weaker
> >	   the defeat.	Where two pairs of options have the same number
> >	   of votes in favor of the defeated option, the fewer votes in
> >	   favor of the defeating option, the weaker the defeat.
> So if we have two defeats A>>B and C>>D, then we lexigraphically compare 
> (|B>A|, -|A>B|) and (|D>C|, -|C>D|)
> What do you mean by "options with the weakest defeat"?

I meant |A>B| and |B>A| where (|B>A|, -|A>B|) is a weakest defeat, 

[I didn't phrase that very will in the draft.]

> My understanding was that we were removing defeats from consideration. 
> If, for example, there were four options A, B, C, D in the Schultz Set, 
> we'd initially be looking at the following set of defeats, in strongest 
> to weakest order:
> A>>B
> A>>D
> B>>C
> C>>A
> D>>C
> B>>D
> After eliminating the weakest defeat (in this case, B>>D, we no longer 
> consider it when determining the Schultz Set, as if we had declared 
> B==D, so that neither B>>D or D>>B held.

In essence, yes.  More specifically, |B>D|=|D>B|=0.

> So what do we really want to eliminate here?

We want to eliminate that option pair from consideration when determining
the next Schwartz set.

> And...
> What if we had |D>C| = |B>D|, |D=C| = |B=D|, |D<C| = |B<D|, so that 
> neither D>>C nor B>>D was weaker than the other?  Do we eliminate both 
> defeats?

Yes -- this is very important if there's only a small number of voters
participating.  Also, I used this in how I phrased the rule to recognize

> >       iii. If eliminating the weakest defeat would eliminate all options
> >	    in the Schultz set, a tie exists and the person with the
> >	    casting vote picks from among these options.
> Hmmm, if we had:
> Defeats = {A>>B, B>>C, C>>A}
> then the Schultz set is {A, B, C}.  Eliminating the weakest defeat 
> (C>>A) would break all the cycles, so !(A>>>A), !(B>>>B), !(C>>>C), so 
> the Schultz set is now empty.  Do we want to the casting-vote-caster to 
> decide in this case, or do we want to say that A wins?

The schultz set is not empty.  A is in the schultz set, and A wins.

> I think it would be better to declare a tie iff all the DEFEATS would be 
> eliminated, not all the options.  Since all the defeats would be 
> eliminated only if they were all of equal strength, there shouln't be a 
> problem.

A tie exists after all defeats have been eliminated, not before.

> >       iv. Otherwise, a new schultz set is found, with those weakest
> >           defeats eliminated,
> >
> >       v. If this new schultz set contains only one option, that option
> >          wins.
> As defined, the Schultz set can't be singleton.  Maybe I'm 
> misinterpreting teh Schultz set.




Reply to: