[EM] smith/schwartz/landau

robert bristow-johnson rbj at audioimagination.com
Sat Mar 24 02:10:29 PDT 2018

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

Subject: Re: [EM] smith/schwartz/landau

From: "Curt" <accounts at museworld.com>

Date: Sat, March 24, 2018 12:20 am

To: "election-methods at lists.electorama.com" <election-methods at lists.electorama.com>



>> On Mar 23, 2018, at 6:36 PM, robert bristow-johnson <rbj at audioimagination.com> wrote:

>> ---------------------------- Original Message ----------------------------


From: "Curt" <accounts at museworld.com>

>> --------------------------------------------------------------------------

>> > https://github.com/tunesmith/condorcet-counter <https://github.com/tunesmith/condorcet-counter>

>> >

>> > I opined a bit in the README but that’s not really the point of the project. I just wanted an easy way to identify Smith and Schwartz sets for myself.



>> to wit: "It's this author's view that a method should only be called a Condorcet if it is limited to identifying the Smith Set,"


>> seems to me that your view is that the current definition of "Condorcet-compliant-method" should be changed. so is Tideman Ranked-Pairs or Schulze Beat-Path methods not "Condorcet methods"?



> Yes, that is my view. They should not be called “Condorcet Methods”, because they are not guaranteed to select the candidate(s) that would defeat all other candidates.


> There is a clear difference between a “Condorcet Method” that finds a Condorcet Winner or Smith Set, and a “tiebreaking" method that tries to pick a single winner from a multi-candidate Smith Set. The latter fails criteria that the former does not. I don’t know what
we should call these tiebreaking algorithms - perhaps they are not quite “tiebreaking” methods since a cycle is not exactly a tie. But it isn’t appropriate to call them “Completion” methods either as that implies something that it isn’t.

> The actual objection I have is that when both are described as “Condorcet Methods”, then it’s too easy in the literature (and the blogs, and the wikipedia articles, particularly from Condorcet detractors) to paint with a broad brush and argue that all Condorcet Methods are
flawed in some manner, same as how all other methods are “unfair” in some way, which ultimately does a disservice to the Condorcet Method. An election that has a Condorcet Winner is not unfair in those ways, compared to something like IRV or Plurality or Top-Two.

> It might worth a survey of what a Smith Set actually *means*. I believe it signifies something valuable about the electorate, beyond just an indication that the election is “incomplete” and that we should apply some algorithm to divine a single winner from it.
well, arguing
about the semantics is one thing, arguing about theory or ideals is another, and arguing about practice is yet another.

so whether you call it "Condorcet-compliant" or call it a turnip, there are ranked-ballot tabulation procedures that are 1. Decisive (they will elect someone) and 2. If a Condorcet Winner exists, the procedure will elect the CW.  we gotta call that something and
"Condorcet-compliant method" is more descriptive than "turnip".  And it serves a purpose.  It separates both practice and "theory and ideals" of these aforementioned procedures from other ranked-ballot systems such as IRV, Borda, or Bucklin.

both Ranked-Pairs and Schulze are fundamentally **not** defined as some post algorithm to divine a single winner from a Smith set that is larger than 1.  They are well-defined procedures, in their own right, that **happen** to elect the CW if a CW exists.  IRV *may* elect the CW if one
exists, but of course we know that hasn't always been the case in practice.  They are not "tiebreaking" a Smith set.  they are not a procedure to be applied **after** it is discovered no single CW exists.  they are procedures that will elect a candidate by the same rules
whether a CW exists or not.  But the candidate elected will be the CW if one exists. So the only practical difference between these turnips is what their outcome might be if there was a Smith set greater than 3 and some weird voting alignment.

So we need a term to draw the line between Ranked-Pairs or Schulze or BTR-IRV on one side and Bucklin, Borda, or IRV on the other.  What semantic would you suggest?

the salient difference is simply what happened in my town 9 years ago: A candidate for mayor was elected to office when the voters in the city unambiguously marked their ballots that they preferred a different **specific** candidate.  that is the problem with **any** non-turnip method. 
it's the converse of who a CW is.  if everyone's vote carries the same weight (this is the "one-person-one-vote" principle), if Candidate A is preferred by more voters than Candidate B, what possible reason in the world should the less-preferred candidate be tapped to serve than the
more-preferred candidate?  especially when **no** other candidate is preferred over the more-preferred candidate?

When at all possible (because it isn't always, at least in theory), if more voters mark their ballots preferring Candidate A over Candidate B than the number of voters marking their ballots to the contrary, then Candidate B is not elected.  What semantic should be used for the previous


r b-j                         rbj at audioimagination.com

"Imagination is more important than knowledge."

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