[EM] The worst about each system; Approval Preferential Voting (new name for an MCA-like system)

[Jameson Quinn]

2010/5/26 Kevin Venzke <stepjak at yahoo.fr>

> --- En date de : Mar 25.5.10, Jameson Quinn <jameson.quinn at gmail.com> a
> écrit :
> What are the worst aspects of each major voting system?
> ...
>
> -IRV: Voting can hurt you (nonmonotonicity). ...
> http://zesty.ca/voting/voteline/ ...
>
> ^
> I don't call this problem nonmonotonicity...
> ^
>
> Whatever you call it, it's obvious when you play with that app I linked to.


>
>
> -Approval: divisiveness. ...
>
> ^... The method here appears to be a game or tool like FPP
> rather than a metric in itself, of who is a good candidate.
> ^
>

You've expressed better than I could why I think Approval lacks legitimacy.


>
> Voters rank each candidate as preferred, approved, or unapproved. If any
> candidates have a majority ranking them at-least-approved, then the one of
> those which is most preferred wins outright.
>
> ^
> This part here has been thought of before: I/we called it MAFP. But
> when no one had a majority then simply the approval winner would win.
> ^
>

Majority Approval First Preference???

>
> If not, then the two candidates which are most preferred against all others
> (ie, the two Condorcet winners based on these simple ballots, or the two
> most-preferred in case of a Condorcet tie) proceed to a runoff.
>
> ^
> This seems not clearly defined to me...? Are you saying the "two most
> preferred candidates" and implying that this is the same as being the
> two Condorcet winners?
> ^
>

No, I mean an actual pairwise analysis, using just the data from these
ballots. The easiest way to do it would be to calculate the "base total" of
preferences plus approvals for each candidate, and then to compare A and B,
you'd subtract from A's base total the number of approvals she got from
B-preferrers, and vice versa, then compare results.


>
>
> I'm having trouble understanding how monotonicity is guaranteed. Suppose
> that there is a runoff between X and Y and X wins. Isn't it possible
> that when X takes some preferences from Y, then instead the runoff is
> between X and Z? Just like a normal runoff. Or is this move not
> considered because it's a three-slot ballot?
>

It's not zero-sum. If some Y-preferrers move X up (either to approval, or to
preferred-along-with-Y), that makes no difference in the question of Y vs.
Z. In other words, the main difference from a normal runoff is that
equalities are allowed. This makes it monotonic.


> Those are the only comments I have at the moment.
> ^
>

Thanks.

Jameson
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