[EM] compromising strategy in Condorcet...

[Jobst Heitzig]

Dear Markus!

you wrote:
> The majority criterion and invulnerability to compromising are
> mutually incompatible. Proof:
> 
> 40 A > B > C. 35 B > C > A. 25 C > A > B.
> 
> Suppose that the used election method meets the majority criterion.
> 
> Suppose that A wins the elections. Then the 35 BCA voters can change
> the winner from A to C by voting CBA (i.e. by compromising).
> 
> Suppose that B wins the elections. Then the 25 CAB voters can change
> the winner from B to A by voting ACB (i.e. by compromising).
> 
> Suppose that C wins the elections. Then the 40 ABC voters can change
> the winner from C to B by voting BAC (i.e. by compromising).
> 
> The above example demonstrates that when there is no Condorcet winner
> and the used election method satisfies the majority criterion then
> there is always an incentive to use a compromising strategy.

It seems I don't exactly know what the "Majority Criterion" is, but
anyway: Don't you implicitly assume resoluteness here? Since the above
situation was exactly the reason for me to propose non-deterministic
methods which will elect either of A,B,C with a positive probability.
Then no majority has an incentive for compromising, at least not when we
assume that noone will vote strategically if s/he thereby risks to get a
worse outcome than before...

Schönen Abend wünscht
Jobst