Kevin,
I had written:
CDTT,IRV is less vulnerable to Burial than Defeat-Dropper(Winning
Votes) or any other plain rankings method that meets
Mutual Majority, Smith(Gross) and Clone Independence.
You helpfully gave this reply to a reply from James G-A:
40 A>B>C (sincere)
25 B>A>C
35 C>B>A
IRV/FPP/DSC order is A>C>B; CDTT is {b}.
40 A>C>B (insincere)
25 B>A>C
35 C>B>A
IRV/FPP/DSC order is A>C>B; CDTT is {a,b,c}.
Yes, CDTT methods have the same burial problem (and solution) as
WV methods. That's one reason I suggest CDTT,RandomBallot.
Thanks for this clarification, which I'd wrongly hinted wasn't true. But
take this really outrageous scenario (one of James G-A's):
46: A>B>C
44: B>C>A (sincere is B>>>>A>C)
05: C>A>B
05: C>B>A
A is the sincere CW, and the (voted) CDTT is {A,B,C}. Pairwise
Defeat-Dropper(Winning Votes) elects the Buriers' candidate B, while
CDTT,IRV easily elects A.
With your suggestion CDTT,Random Ballot the Buriers increase the chance
of their favourite winning from zero to 44%. This is a huge bargain for
them if their sincere ratings
gap between their second and last preference is much smaller than the
one between their first and second preference. (In any case, here the
chance of their sincere last preference
being elected only rises from zero to 10%).
So on balance I don't think CDTT,RB really resists Burying better than
CDTT,IRV.
Chris Benham
----
Election-methods mailing list - see http://electorama.com/em for list info
