[EM] Advantage of MDDA over Approval?

[Kevin Venzke]

Jan,

--- Jan Kok <jan.kok.5y at gmail.com> a écrit :
> I'm having a hard time wrapping my head around MDDA, partly because
> I'm not sure about the definition.  A candidate A must be ranked lower
> than some _specific_ candidate B on a majority of ballots in order to
> disqualify A ("ranked lower" would include A not appearing on a ballot
> while B appears on the ballot), is that right?

Yes. If A>...>B on more than half the ballots, B is disqualified, unless
this would result in all candidates being disqualified.

> So, what is the advantage of MDDA over Approval?  If some candidate
> has majority first-choice support, then that candidate will win in
> almost any system.

MDDA satisfies majority favorite, Ossipoff's SFC, and Woodall's
Condorcet(gross).
Also, it satisfies SDSC, which technically Approval can't because it isn't
a rank method.

On the downside, MDDA doesn't satisfy plurality, participation, or
Later-no-help.

>If no candidate has majority first-choice support,
> then MDDA is just Approval.

No, MDDA is just Approval if either no one or everyone has a
majority-strength
pairwise loss.

>  If more than one candidate gets more than
> 50% approval votes, I would think it would usually be because of
> second-choice votes for a compromise candidate, and the compromise
> candidate would likely win, same as Approval.
> 
> I think the main technical problem with Approval is that it can be
> difficult to decide whether to vote for compromise candidates in
> addition to ones favorite.  Does MDDA help?

MDDA helps somewhat. If it turns out that your favorite has a
majority-strength
win over your second choice, your favorite could win despite your approval
of your second choice.

I think ICA does a better job. It almost satisfies Condorcet, so that your
favorite's win over your second choice doesn't need to be a majority win.

Kevin Venzke



	

	
		
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