[EM] "Completion" & falsification

Kevin Venzke stepjak at yahoo.fr
Wed Jan 21 14:55:03 PST 2004


I think you may be confused about the process of Symmetric Completion 
as different from the criterion.  The criterion says that the method
gives the same results whether or not the ballots are completed
symmetrically.  This is met by FPP, IRV, and Margins, none of which
employ the *process* of Symmetric Completion.

(FPP and IRV meet SC mainly because they only permit equal ranking through
truncation.  Margins meets it because the SC process would not alter
the margin of any victory.)

So if we are talking about the merits of Symmetric Completion as a
criterion, it is irrelevant whether Symmetric Completion is objectionable
as a process performed on the ballots, because the criterion doesn't
depend on the process.

More below...

 --- MIKE OSSIPOFF <nkklrp at hotmail.com> a écrit : > 
> Chris said:
> indifferent between B and C,
> and one votes
> [1]A > [ ]B > [ ]C
> and the other votes> [1]A > [2]B > [2]C
> then in my humble opinion, it is common-sense (and reasonable) for those two 
> voters to expect that
> their votes would  have the same effect ("be treated in the same way", as 
> Woodall puts it).
> MO replies:
> They're both expressing exactly the same set of pairwise preferences. But 
> that isn't an example of "symetrical completion". Your "symetrical 
> completion" would have the A only voter voting AB and also voting  AC. 
> Indicating two opposite preferences. One of those 2 opposite preferences is 
> an order-reversal, or else they're both falsified preferences. Falsified not 
> by the voter, but by you.
> Any Condorcet version that I've heard of would count those 2 ballots as 
> voting the same pairwise preferences. That example isnt about the matter of 
> "symetirical completion".

Actually, I don't know why Chris used that example.  I think this example
is clearer: According to the mentality of Symmetric Completion (criterion),
two voters voting A=B>C>D should have exactly the same effect as one of
the two voting A>B>C>D and the other voting B>A>C>D.

If Mike thinks this is flawed thinking, it would be interesting to hear
what he thinks the difference in effect should be.

> You continued:
> If the method allows equal early preferences, then it is unfair (and in my 
> opinion absurd and very
> bad) that a faction of voters that all vote a set of candidates above all 
> other candidates should
> be advantaged or disadvantaged (at least on average) by voting equal 
> preferences.
> I reply:
> It isn't at all clear what you're talking about. A guess would be that 
> you're implying that somehow a faction of voters that all vote a set of 
> candidates over all the other candidates is advantaged or disadvantaged if 
> their ballots aren't falsified by you. But maybe that isn't what you mean; 
> its only a guess.

My interpretation is that a faction shouldn't spoil the election for themselves
because they opt to express strict preferences among their favorites, instead of
using approval strategy.

> Say a voter refuses to express a preference between X and Y. Anyone who says 
> that that voter is saying that s/he prefers X to Y, and that s/he also 
> prefers Y to X, must have their head all the way up their ass.

It's not necessarily saying that.  The idea is that the effect should be the

The way Chris' method uses SC is equivalent to handling equal rankings in
IRV by awarding fractions of the ballot's traveling vote.  He could have
specified that instead.

Kevin Venzke
stepjak at yahoo.fr

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