[EM] My Favorite Deterministic Condorcet Efficient Method: TACC

[C.Benham]

Chris wrote ...

>/ 31: A>B
/>/ 32: B>C
/>/ 37: C>A
/>/
/>/ Approvals: B63, A68, C69. A>B>C>A.
/>/
/>/ TACC elects A, but C is positionally the dominant candidate and
/>/ pairwise beats A.
/>/
/>/ For a Condorcet method with pretension to mathematical elegance,
/>/ I don't/ /see how that/ /can be justified.
/>/
/>/ Chris Benham
/>/
/>/ PS: Could someone please refresh our memories: What is the
/>/ "Banks Set"?
/
Forest Replies:


>As you know C is the DMC winner, and would be a slightly better winner, given
>that the ballots are sincere.  But DMC is not as burial resistant and truncation
>resistant as TACC.  
>
>It is interesting that DMC and TACC have opposite rules for which of the top two
>approval members of the top cycle (of three) wins.  DMC awards the win to the
>one (of these two) that beats the other.  TACC awards the win to the one that is
>beaten by the other.


Chris: 
I have long since abandoned the  "Definite Majority Choice" (DMC) method in
favour of Smith//Approval (as my preferred Condorcet method), which also elects C 
here.

I still like the Definite Majority criterion, which says that no candidate that is
pairwise beaten by a more approved candidate is allowed to win.

I think that (in isolation) meeting the Condorcet criterion is desirable, but not so
holy that on discovering there is no voted CW the method should proceed on the assumption
that there is really a "sincere CW" that has been victimised by strategists the method
should try to frustrate or punish.

Condorcet methods are vulnerable to Burial, period. Futile attempts to address this
should not be at the expense of producing winners that can have no philosophical
justification on the assumption that all the votes are sincere (or are all equally
likely to be sincere).

The TACC winner A simply has no shred of justification versus the Smith//Approval
winner C.

Forest:

>I've come around to the belief that most Condorcet cycles in ordinary elections
>are artificial, so chances are that this cycle was created from the burial of B
>by the C faction.  Giving C the win only rewards this manipulation.


Chris:
I can't see any remotely rational justification for assuming that this is the case
rather than, say, the cycle was created by the A voters burying C.

BTW, I also like the version of Smith//Approval that allows voters to indicate an
approval threshold so they can rank among approved candidates.

I think on balance I prefer IBIFA to any of the Condorcet methods.

Thanks for explaining the Banks Set. I'll look more into it.


Chris Benham















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