[EM] 3 or more choices - Condorcet

[robert bristow-johnson]

this is a resend.  it's been hours since i first posted this and it 
hasn't shown up on the list.

On 11/8/12 11:55 AM, Chris Benham wrote:
> Robert Bristow-Johnson wrote (1 Oct 2012):
>
> "my spin is similar.  Ranked Pairs simply says that some "elections" (or
> "runoffs") speak more loudly than others.  those with higher margins are
> more definitive in expressing the will of the electorate than elections
> with small margins.  of course, a margin of zero is a tie and this says
> *nothing* regarding the will of the electorate, since it can go either
> way.
>
> the reason i like margins over winning votes is that the margin, in vote
> count, is the product of the margin as a percent (that would be a
> measure of the decisiveness of the electorate) times the total number of
> votes (which is a measure of how important the election is).  so the
> margin in votes is the product of salience of the race times how
> decisive the decision is."
> Say there are 3 candidates and the voters have the option to fully
> rank them,
> but instead they all just choose to vote FPP-style thus:
>
> 49: A
> 48: B
> 03: C
> Of course the only possible winner is A. Now say the election is held
> again (with
> the same voters and candidates), and the B voters change to B>C giving:
>
> 49: A
> 48: B>C
> 03: C
>
> Now to my mind this change adds strength to no candidate other
> than C, so the winner
> should either stay the same or change to C. Does anyone disagree?
> So how do you (Robert or whoever the cap fits) justify to the A voters
> (and any fair-minded
> person not infatuated with the Margins pairwise algorithm) that the
> new Margins winner is B??
> The pairwise comparisons: B>C 48-3,  C>A 51-49,  A>B 49-48.
> Ranked Pairs(Margins) gives the order B>C>A.
>
> I am happy with either A or C winning, but a win for C might look odd
> to people accustomed
> to FPP and/or IRV.
> *If* we insist on a Condorcet method that  uses only information
> contained in the pairwise
> matrix (and so ignoring all positional or "approval" information) then
> *maybe* "Losing Votes"
> is the best way to weigh the pairwise results. (So the strongest
> pairwise results are those where
> the loser has the fewest votes and, put the other way, the weakest
> results are those where the
> loser gets the most votes).
> In the example Losing Votes elects A. Winning Votes elects C which I'm
> fine with, but I don't
> like Winning Votes for other reasons.
>


well, i'm not the guy with upper-case letters.  i didn't comment on this 
response to what i said, but looking it over right now, whether people 
vote on a Ranked-Choice ballot as if it were FPP or not, any candidates 
*not* ranked are tied for last place on that ballot.  so

49: A
48: B
03: C

is really
49: A>B  A>C
48: B>A  B>C
03: C>A  C>B


the difference with this:

49: A
48: B>C
03: C

is that C gets a helluva lot more support from B voters than the other 
scenario.

49: A>B  A>C
48: B>C>A
03: C>A  C>B

it's the same old complaint that Rob Ritchie (FairVote) and others make 
against Condorcet (justifying putting all their support behind IRV): 
that (from their POV) Condorcet can elect wishy-washy candidates with 
little primary support.  i (and Condorcet) would say that in the second 
case, C is the best candidate even if he/she got only 3 first-choice 
votes.  might be a nice centrist, no-drama candidate in a polarized 
environment.  in Burlington VT 2009, the 3rd-place finisher from the POV 
or FPP or IRV was the Condorcet winner and nearly everyone i talked with 
would have been much happier with this candidate than with whom actually 
won the IRV or with whom would have won FPP (who suffered a decisive 
defeat in a repeat run in March 2012).  but the margins weren't so wide 
as with this example, candidate C got a lot more than 3% primary support 
votes.

again, i will repeat that probably, technically, Schulze is superior to 
Ranked-Pairs.  but it doesn't matter with a Smith Set of 3 candidates or 
less.  Condorcet cycles will be rare.  cycles with more than 3 in the 
Smith set will be rare of the rare.  it's best to get Condorcet of 
*some* method enacted into law.  the most realistic path to 
accomplishing that is *not* to advocate a method that cannot be 
explained to citizen-legislators.  and i still think that margins is 
better than either winning votes (or the logical complement regarding 
the most losing votes).  margins encompasses *both* winning votes and 
losing votes (the latter with a negative sign, of course).

-- 

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."