[EM] Hay guys, look at this...

[Colin Champion]

I think Robert was wise to propse Condorcet+FPTP. It's the Judgement of 
Solomon, allowing him to step aside from endless debates about which 
Condorcet method is best.
    I don't agree with his reasoning "If a simple majority of voters 
mark their ballots preferring Candidate A over Candidate B... Why should 
B be elected?" This is the argument of the Condorcet Loser Criterion, 
which implicitly assumes that a decision can be determined purely by the 
signums of the margins, ignoring their amplitudes. Minimax violates 
Condorcet Loser and I'm not the only person to support it.
    But then I don't favour Kristofer's proposal either. My evaluation 
suggests that burial is a particular threat for Condorcet methods, and 
that in its presence their accuracies are: minimax 64%, condorcet+fptp 
59%, copeland,fptp 48%. [Usual disclaimers apply.]

[I would say a word in favour of SPE with an FPTP preranking. This is a 
symmetrisation of the method of Llull's De Arte Eleccionis of 1299, so 
it's essentially the oldest Condorcet method in existence which isn't 
vitiated by indecisiveness. Its virtue lies in its linear-time 
countability, which is only a factor if counting is manual and there is 
a risk of a sizeable number of candidates standing. SPE is about as 
resistant to burial as is minimax.]

Wiser judgements than Solomon's are imaginable. If there was a an expert 
consensus that among those methods simple enough to gain the approval of 
voters and legislators, XYZ was best, then Robert would probably listen; 
but the onus is on experts to build a consensus, not on advocates to 
take sides.

CJC


On 18/02/2023 06:05, Forest Simmons wrote:
> Let me rephrase the question ... suppose that there were only three 
> candidates and you already knew that they were in a rock paper 
> scissors pairwise preference cycle.
>
> How would you decide which one to vote for if you could only vote for one?
>
> That's the one you should make your first choice on an RCV ballot if 
> the cycle breaker is FPTP as you have been suggesting.
>
> That decision is at least as difficult as the approval decision would 
> be, because under approval strategy you should approve that candidate 
> X (the one you would vote for if you had only one vote) AND also 
> approve your favorite if X was not already your favorite.
>
> These are the same candidates that you would naturally rank on an RCV 
> ballot ... leaving the 3rd choice unranked ... the one that is neither 
> your favorite nor your compromise.
>
> If you mis-triangulate the compromise in an FPTP election ... too bad: 
> you wasted your vote. But the approval ballot also counts towards 
> everybody you like better than your compromise, including your favorite.
>
> That's why Approval is often proposed as a Condorcet completion method 
> in the absence of a runoff.
>
> Implicit approval takes advantage of the natural strategy of 
> truncating the candidates you don't like, while ranking your preferred 
> of the two front runners AND anybody you liked better ... including 
> your favorite ... whether or not it was a frontrunner.
>
> Yes, the cycle is already there ... but it cannot split the votes 
> unless the method allows vote splitting by not having any contingent 
> backup vote. Approval has the simplest backup vote capability ... any 
> other method requires some kind of runoff/elimination step to 
> ameliorate the potential vote split.
>
> Example ballot profile:
>
> 40 A>B (Sincere is A>C)
> 35 B>C
> 25 C>A
>
> Under Plurality A wins.
>
> The Implicit Approval (fewest truncations) winner is B with only 25 
> truncations, compared with 35 A truncations and 40 C truncations.
>
> This is a typical kind of ballot profile resulting from the burial by 
> the largest faction ... of the sincere Condorcet Winner (C in this 
> example).
>
> If the C supporters wanted to protect C, they could have truncated A:
>
> 25 C instead of 25 C>A.
>
> This would not change the Plurality winner, but reinforces the 
> Implicit Approval winner, which gives the sincere CW a defense against 
> burial by punishing the burying faction ... electing their sincere 
> last choice instead of their sincere second choice.
>
> With this defensive truncation B still has the fewest truncations 25, 
> but now the burial perpetrator A has way more truncations (60) than 
> either of the others ... no chance of success in their burial gambit.
>
> Electing the Plurality choice (lacking a ballot CW) rewards the burial 
> perpetrator in this example .... so it encourages candidates with 
> large first place support to bury the sincere CW.
>
> This example is typical in this respect ... the insincere  burial (of 
> sincere CW) gambit is most tempting to the faction with the greatest 
> first place support.
>
> On the other hand it is not tempting to bury the CW when lacking a CW 
> the implicit approval candidate is elected ... because this burial 
> gambit will almost certainly fail if not outright backfire.
>
> It seems to me that anybody who understands why Approval is superior 
> to FPTP Plurality as an election method ... such a person should be 
> able to see how Approval is a better fall back alternative than 
> Plurality (absent a CW) .... an appreciable positive difference at no 
> extra cost.
>
> The little Dutch boy was right to put his finger in the dike ... a 
> stitch in time is in deed worth nine.
>
>
>
>
>
>
>
> On Fri, Feb 17, 2023, 7:07 PM robert bristow-johnson 
> <rbj at audioimagination.com <mailto:rbj at audioimagination.com>> wrote:
>
>
>
>     > On 02/17/2023 9:44 PM EST Forest Simmons
>     <forest.simmons21 at gmail.com <mailto:forest.simmons21 at gmail.com>>
>     wrote:
>     >
>     >
>     > Suppose the whole election was to choose one of the three
>     candidates ... no noncycle members were in the election at all.
>     >
>     > Would you recommend FPTP Plurality over Approval?
>     >
>     >
>
>     I dunno.  I would recommend Condorcet RCV and, only in the
>     super-rare case of a cycle, I would recommend plurality of
>     first-choice votes because it's no worse than we already have now
>     with FPTP and it's simple to explain to voters why that one
>     candidate (the one with more first-choice votes than anyone else)
>     is, in some sense, uniquely more preferred by the electorate over
>     any other candidate.
>
>     In a competitive 3-way race, I dunno if Approval would be better
>     than FPTP.  I *do* know, if it were Approval, that I would have a
>     tactical decision to make regarding my second-favorite candidate.
>
>     But with RCV, I would have no tactical decision to make.  I would
>     know immediately what I would do with my second-fav.
>
>     --
>
>     r b-j . _ . _ . _ . _ rbj at audioimagination.com
>     <mailto:rbj at audioimagination.com>
>
>     "Imagination is more important than knowledge."
>
>     .
>     .
>     .
>
>
> ----
> Election-Methods mailing list - see https://electorama.com/em for list info

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