[EM] Does IRV elect "majority winners?"
markus.schulze at alumni.tu-berlin.de
Fri Jan 2 08:32:38 PST 2009
Dear James Gilmour,
you wrote (2 Jan 2009):
> So let's try a small number of numbers.
> At a meeting we need to elect one office-bearer
> (single-office, single-winner). There are four
> candidates and we decide to use the exhaustive
> ballot (bottom elimination, one at a time) with
> the requirement that to win, a candidate must
> obtain a majority of the votes.
> First round votes: A 40; B 25; C 20; D 15.
> No candidate has a majority, so we eliminate D.
> Second round votes: A 47; B 25; C 20.
> It seems that some of those present who voted
> for D in the first round did not want to vote in
> the second round - but that is their privilege.
> QUESTION: did candidate A win at the second round
> with 'a majority of the votes'?
I wrote (2 Jan 2009):
> Whatever the statement "the winner always wins a
> majority of the votes" means, this statement must
> be defined in such a manner that you only need to
> know the winner for every possible situation (but
> you don't need to know the used algorithm to
> calculate the winner) to verify/falsify the
> validity of this statement. Otherwise, this
> statement is only a tautology.
You wrote (2 Jan 2009):
> Markus, I don't know where the statement "the
> winner always wins a majority of the votes" came
> from, but it is not mine, and in my opinion, it
> does not take the discussion any further forward..
> What I wrote, very specifically, was "with the
> requirement that to win, a candidate must obtain
> a majority of the votes." Statements of this kind,
> and in these words (or words almost identical
> to these), are used when elections are held at
> meetings and are conducted either by show of
> hands or by informal paper ballot This form of
> words distinguishes such elections from those
> where a single-round plurality result would be
> accepted, when the corresponding statement from
> the Returning Officer would be something like
> "and the winner will be the candidate with the
> most votes".
> This thread is about the meaning of the
> expression "a majority of the votes".
> I presented the simple scenario above to see
> what views there might be about the meaning of
> "a majority of the votes" in that specific
This thread is rather about the meaning of the
expression "to win a majority of the votes".
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