[EM] Condorcet question - why not bullet vote

[Peter Zbornik]

Juho,

we have the example
49: A
48: B>C
3: C>B

you wrote to me:
"- C loses to B, 3-48. In winning votes the strength of this loss is 48.
- B loses to A, 48-49. In winning votes the strength of this loss is 49.
- A loses to C, 49-51. In winning votes the strength of this loss is 51."

Thus: "If the three C voters will truncate then they will win instead of B
in winning votes based Condorcet methods."

This is correct, if proportional completion is not used (see page 42 in
http://m-schulze.webhop.net/schulze2.pdf)
If proportional completion is used (which I would recommend) then B wins.

If proportional completion is used, then we need to fill in the preferences
of the ones who did not vote:
We have 100 voters.
- C loses to B, 3-48, means 49 voters did not vote. We split each voter into
two: the first has weight 3/51 of a vote and the second 48/51, which gives a
total score of 49*3/51+3 vs 49*48/51+48
- B loses to A, 48-49, means 3 voters did not vote. We split each voter into
two: the first has weight 48/97 and the second 49/97, which gives a total
score of 3*48/97+48 vs 3*49/97+49
- A loses to C, 49-51, means all voters voted.

Thus after the proportional completion, the vote tally is the following:
- C loses to B, 5,88-94,12. In winning votes the strength of this loss
is 94,12.
- B loses to A, 49,48-50,52. In winning votes the strength of this loss
is 50,52. (delete this link first)
- A loses to C, 49-51. In winning votes the strength of this loss is 51.

Thus B wins if proportional completion is used. C wins without proportional
completion.

Best regards
Peter Zborník

On Wed, Jun 16, 2010 at 9:35 PM, Juho <juho.laatu at gmail.com> wrote:

> On Jun 16, 2010, at 9:39 PM, Peter Zbornik wrote:
>
>  In what situations will bullet voting help my candidate to win
>> (considering the advanced Condorcet systems)?
>>
>
> Here's one more example where a reasonably small number of strategic voters
> can change the result.
>
> 49: A
> 48: B>C
> 3: C>B
>
> If the three C voters will truncate then they will win instead of B in
> winning votes based Condorcet methods.
>
> Juho
>
>
>
>
>
>
> ----
> Election-Methods mailing list - see http://electorama.com/em for list info
>
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