[EM] Truncation (was re: Defeat Strength)

[robert bristow-johnson]

> On 09/10/2022 9:25 AM EDT James Gilmour <jamesgilmour at f2s.com> wrote:
> 
>  
> I think there is a lot of misunderstanding in this discussion under the Defeat Strength heading, now Truncation.

We realize that you think that.  It's quite apparent.

>  I suspect it may arise from a confusion of "IRV" with "preferential voting".  IRV = Single Transferable Vote applied to a single-winner election (= Alternative Vote in the UK) uses preferential voting, but there are several (many?) other ways of counting the votes recorded on ballot papers marked with voters' preferences.

So where is the source of that confusion.  The document you had attached says "This method of filling a single vacancy is commonly called the Alternative Vote. It also known as Preferential Voting or Instant Run-off Voting."

>  You could use a Borda count, or a Condorcet count, or several different 'social choice' methods.

Now, let's exclude the cardinal methods: Score, STAR, Approval from these "several different 'social choice' methods" to remove these from the semantics.  We are talking about ordinal methods; these are methods that use only a ranked-order ballot.

As far as I can tell, there are four basic classes of ranked-order methods:
   1. Borda count
   2. Bucklin voting
   3. Hare STV (IRV etc., FPTP is a degenerate case)
   4. Condorcet (several methods, some invented by persons present)

I don't know any others.  Within each method, what do each of those marked ballots mean?  That is not the same question as asking "How are these ballots tabulated?"

>  All have different implications for the "meaning" of preferences and the "meaning" of truncation (i.e. where the voter has not marked a preference against one or more candidates).
> 

No, that is misinformation.  And we can prove it using simple logic and comparing the manner that the ranked ballot is tabulated using these different ordinal methods.

In *each* of those methods, if Candidate A is ranked higher than Candidate B, then that voter intends to vote for Candidate A, not B, if it were a simple two-person FPTP election.  That's all that can be inferred of the voter's intent from the marks on the ballot.

This is also true; in *each* of these methods, if Candidate A is ranked and Candidate B is not ranked.  We know, from the marks on that ballot, that the voter intends to vote for Candidate A, not B, if it were a simple two-person FPTP election.  That can be and is all that can be inferred of the voter's intent from that marking of the ballot.

I define "the truth" to be an accurate description of reality.  The above two paragraphs are true.

>From that, there is *no* operational difference between a candidate that is unmarked and a candidate that is ranked at the very bottom if there are no other candidates unmarked.  So the sole unranked candidate is esteemed by the voter equivalently to that candidate being ranked at the very bottom.  Every other candidate is preferred by the voter over that bottom-ranked or sole unranked candidate.  The voter intends to vote for *any* of the ranked (or higher-ranked) candidates and not that unranked (or bottom-ranked) candidate in *any* simple two-candidate FPTP election.

Then the next thing to do is consider more than one unranked candidates.  Some, not all, ranked-choice (or ordinal) methods allow for equal ranking of candidates.  That difference *is* relevant to the specific method, but all methods (in jurisdictions that don't force voters to rank each candidate) allow for any number of unranked candidates.  In the case where equal ranking is allowed, there is *no* operational difference between those candidates being unmarked and those candidates being equally ranked at the very bottom.

That means, in ordinal (ranked-choice) voting, that unranked candidates are consistently interpreted as being tied for the lowest, bottom ranking.  But there is no difference, in voter intent, between the same ballot in an ordinal method that disallows equal ranking versus being in an ordinal method that allows equal ranking.  What the voter's expressed preference is essentially the same.  The voter intends to vote for *any* of the ranked (or higher-ranked) candidates and not for that unranked (or bottom-ranked) candidate in *any* simple two-candidate FPTP election.

All that disallowing equal rankings means that, if not ranking is also disallowed, the voter would be forced to choose between unranked candidates, which unranked candidate is preferred over which other unranked candidate.  But, still, any of those previously unranked candidates that now the voter is forced to rank, will be ranked lower than any of the previously ranked candidates.  In a simple two-candidate FPTP election, the intent of the voter is unchanged between any of the previously ranked candidates and any of the previously unranked candidates.  We know who the voter is voting for.

> What we are not at liberty to do is to take some aspect of the imputed philosophy of these other methods and say that it applies to IRV, or that it should apply to IRV.

And I did none of that above.

>  IRV is IRV,

and tautologies are tautologies.  That's true, but is what some might label an empty truth.

> ... and there is nothing in the Election Rules for an IRV count (attached) that says anything about the "meaning" of multiple blanks (no preferences against several candidates) other than that voter prefers the marked candidates to all and any of the unmarked candidates and that voter has no preference AMONG the unmarked candidates.

Well, "nothing in the Election Rules for an IRV count that says anything about the 'meaning'", but the Election Rules do not have the ability to remove the operational implication of the relationship between the ranked and unranked candidates.  In any ranked ballot, the meaning is the same: That voter prefers *any* ranked candidate over *any* unranked candidate.  And that is operationally equivalent to the same ballot where unranked candidates are tied for the lowest preference.

>  If the count proceeds such that the next IRV exclusion has excluded (eliminated) all of a voter's marked candidates, the Returning Officer declares that ballot paper 'non-transferable' and that voter takes no further part in deciding the outcome of the election.
> 

That's about the function of the election.  It still changes nothing about the meaning of the marked ballot.  And the meaning of the marked ballot is as I said above: If A is ranked higher than B or if A is ranked and B is unranked, if the election was a simple two-candidate First-Past-The-Post election, that voter is voting for A and not voting for B.

James, you may have a doctorate.  You may live on the island where the notion of the single-transferable vote was birthed.  But when you keep repeating:

> I think there is a lot of misunderstanding in this discussion...

> ...based on a serious misunderstanding of how STV-PR works,...

... then you are betraying your misunderstanding.  Not mine.

And when you claim:

> Where a voter does not mark a preference against every candidate, that voter [means] that he or she has no preference among the unmarked candidates, and that if any choice has to be made among those candidates, he or she is happy to leave that decision to those voters who do have preferences among those candidates.

That's true.  But when you claim:

>  Unmarked preferences mean nothing more than "I have opted out at this point and leave any further decisions to others".

That's false.  The unmarked preferences *do* mean something more.  They means that the voter prefers (and would vote for) *any* of the marked candidates over *any* of the unmarked candidates.

And that is operationally equivalent to equally-ranking all of those unmarked candidates at the very lowest ranking level on the ballot.

--

r b-j . _ . _ . _ . _ rbj at audioimagination.com

"Imagination is more important than knowledge."

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