[EM] How close can we get to the IIAC (=> "in the absence of cyclic preferences")
Kristofer Munsterhjelm
km-elmet at broadpark.no
Mon Apr 19 01:11:21 PDT 2010
Juho wrote:
> On Apr 19, 2010, at 10:46 AM, Kristofer Munsterhjelm wrote:
>> The same is true of, for instance, LNHarm. If X is the CW, then if a
>> subset of the voters add Y to the end of their ballots, that won't
>> make X a non-CW. However, it's also possible to show that no matter
>> how the Condorcet method behaves in the case of a cycle, one can
>> construct an example where the method fails LNHarm.
>
> Your last sentence contains word "cycle". Were you thinking about IAC in
> the sincere opinions only or also in the actual votes? (If needed one
> can handle separately cases where IAC applies to sincere opinions only
> vs. both sincere opinions and actual votes.)
No, that was a brief departure from IAC. The point was to show that even
though Condorcet methods pass LNHarm in the "non-cycle" case, the
Condorcet compliance itself introduces a discontinuity of sorts, which
means that the method as a whole (with ballots that may be cyclic or
not) cannot pass LNHarm.
In other words, I was answering, in advance, a possible reply of "but if
a Condorcet method can pass LNHarm inside the acyclical domain, then all
we have to do is to align the cyclical domain propely, and we'll have a
LNHarm Condorcet method, no?".
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