[EM] SSFC is attainable if we accept 0-winner outcome. Maybe if we don't?

[MIKE OSSIPOFF]

Not only is SSFC attainable at that price, but so is this more ambitious 
criterion:

Strong Sincere Strategy Criterion (SSSC):

If a majorilty prefer X to Y, and vote sincerely, then Y shouldn't win.

[end of SSSC definition]

Here's a method that meets SCCC and SFCC (any method that meets SSSC meets 
SFCC):

Ranked Majority Defeat Disqualification (RMDD):

Balloting: Rank balloting
The voter may rank as many candidates as s/he wants to.
Equal rankings and truncation are allowed.

A candidate loses if a majority vote another candidate over hir.

[end of RMDD definition]

As I define sincere voting, and with RMDD's balloting, anyone who prefers X 
to Y and votes sincerely votes X over Y.

And so if a majority prefer X to Y and vote sincerely, then, by RMDD's 
rules, Y loses.

But RMDD is indecisive. It can return a tie in which there are several 
winners, or a tie in which there are zero winners. Of course a tiebreaker 
could be used, but if a 0-winner tie is solved and someone is elected, then 
SSSC compliance is lost. Since the method can't identify a CW who has a 
defeat, SSFC complilance is lost too.

That's also why we can't define a method that says: Any candidate with a 
majority defeat by the CW loses.

The method has no way of identifying a CW who has a defeat.

But does that mean that if we insist on a winner, SSFC compliance is 
unattainable? Maybe not. Though the method's rules can't specifically refer 
to the CW, that doesn't mean that a method can't meet a criterion that 
refers to the CW. SFC and  (my) CC show that.

So, can anyone show that SSFC is unattainable if we insist on a winner? Or 
suggest a method that might meet SSFC and always returns a winner?

Let me repeat the definition of SSFC here:

If a majority prefer the CW to Y, and vote sincerely, then Y shouldn't win.

[end of SFCC definition]

That's SFC, without the clause "If no one falsifies a preference...".

Compliance with SSFC would mean that a method is strategy-free, for a 
majority, for protecting the CW's win from being taken by a less-liked other 
candidate, without having to stipulate that no one falsifies a preference.

Mike Ossipoff

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