[EM] MCA on electowiki

[Jameson Quinn]

2010/10/18 Kathy Dopp <kathy.dopp at gmail.com>

> On Mon, Oct 18, 2010 at 7:06 PM, Jameson Quinn <jameson.quinn at gmail.com>
> wrote:
> > Because by simply voting (participation), you change the threshold needed
> > for an absolute majority, and thus for certain kinds of wins. You cannot
> do
> > this by changing your vote (monotonicity).
>
> But  Statement of Participation Criterion that you linked to says:
>
> Adding one or more ballots that vote X over Y should never change the
> winner from X to Y.
>
> so failing the criteria means adding more votes having X > Y would
> change the winner from X to Y.  i.e. failing monotonicity.
>
> Kathy


This is not the definition of monotonicity. Monotonicity states that
changing an existing vote from X≤Y to X>Y should not change the winner from
X to Y. It says nothing about adding new X>Y votes.

Clearly, the two ideas are related. However, MCA's failures of the "Combined
Monotonicity and Participation Criterion" are limited to the rare
"participation-type" failures, not the potentially more common
"monotonicity-type" failures. (This goes for all stated versions of MCA)

JQ
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