[EM] Defeat strength, Winning Votes vs. Margins, what to do with equal-ranks on the ballot?

robert bristow-johnson rbj at audioimagination.com
Wed May 22 15:14:25 PDT 2019

---------------------------- Original Message ----------------------------

Subject: Re: [EM] Defeat strength, Winning Votes vs. Margins, what to do with equally-ranks on ballot?

From: "Chris Benham" <cbenhamau at yahoo.com.au>

Date: Wed, May 22, 2019 2:35 pm

To: election-methods at lists.electorama.com


> Another Condorcet-compliant method that might interest you, from a Kevin

> Venzke webpage:


>> *Jobst Heitzig's River method* is identical to Tideman's method,

>> except that one additionally ignores (without locking) defeats against

>> candidates against whom some defeat has already been locked. This is

>> possibly the easiest of the three to work out by hand.
maybe someone needs to explain this more to me.  i can think of a plausible example where it may differ from RP, but i can't think of what the motivating principle is.  if River and RP disagree, why is the River winner a
better choice?

> The other two he is referring to are Schulze and Tideman RP. Nearly all

> the time it will elect the same candidate and as far as I know is at

> least as good.
well, we know when there are only 3 in the Smith Set, that Schulze and Tideman pick the same winner.  dunno about this River method, though.

> I strongly suggest that the measure of defeat strength should be Losing

> Votes and that ballots that equal-rank A and B above bottom should

> contribute a whole vote

> to each in the A-B pairwise comparison. Ballots that rank A and B

> equal-bottom (or truncate both A and B) should contribute nothing to the

> A-B pairwise comparison.
that's an interesting proposal i hadn't heard before.  i'll be interested in hearing the motivation of it.  i presume you mean that the defeat strength should be a strictly decreasing function of the losing votes, perhaps -LV (and the greatest
defeat strength is the least negative -LV).  in principle, why is this better than Winning Votes or Margins?  (seems like Margins is the midpoint compromise between WV and LV since it is WV-LV.)
> I'll be posting more on this soonish, but since you asked the question
> thought I'd just give you some food for thought to be going along with.
i am digesting.
Thank you, Chris.


r b-j                         rbj at audioimagination.com

"Imagination is more important than knowledge."

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