[EM] Re: SCRRIRVE & my example
nkklrp at hotmail.com
Fri Jan 23 01:29:01 PST 2004
Here is an example that Mike Ossipoff posted (Tues.Jan.20)
Presumed sincere preferences:
100 ballots. B is the Condorcet Winner (and the IRVE winner).
A voters Bury (offensively order-reverse against)B, while all other voters
Let me just point out that the term "offensive order-reversal" was in use
for years before Blake renamed it "burying". Brevity is convenient, but the
trouble with "burying" is that sometimes one can bury defensively,
sometimes offensively, and "burying" doesn't distinguish those, except for
the reason that Blake probably defines 'burying' as offensive
order-reversal. For instance defensive burying is needed in Approval and
margins. I'm not objecting to "burying", since it's briefer, but I just
wanted to point out which term was in use first, and the meaning fault that
All candidates in the Schwartz set. B>A>C>B.
RP, Beatpath, Simpson, Raynaud all elect A.
SCRRIRVE eliminates A and elects C, so the A voters' strategy back-fires.
I guess Chris didn't get what I said the other day: All you've proven with
the example is that uncountered offensive order-reversal can succeed in wv
(whether the method is MAM, BeatpathWinner, or any other wv version).
But no one here has denied that offensive order-reversal can succeed in wv.
In fact, offensive order-reversal can succeed in every method that doen't
have a worse problem.
(For instance, IRV & Plurality have worse problems).
Certain desirable properties can't be gotten without looking at pairwise
preferences. That admits the possibiilty of offensive order-reversal making
a cycle of pairwise preferences. A symmetrical cycle in which no method can
distinguish order-reversers' candidate and CW.
So, since no one denies that wv (like all methods that don't do something
worse) can let offensive order-reversal succeed, the purpose of the example
is in doubt.
The example, as I explained before, doesn't show that SCCIRVE doesn't ever
let offensive order-reversal succeed.
Will Chris demonstrate that offensive order-reversal can't succeed in
SCCIRVE? Will Chris at least demonstrate that SCCIRVE has a counter strategy
that will prevernt SCCIRVE from succeeding--a coutnerstrategy other than
defensive favorite-burial? And will Chris demonstrate that, in some way,
SCCIRVE is truncation-resistant? If truncation can easily steal the election
from the CW in SCCIRVE, then what is it worth if, in one example, offensive
order-reversal doesn't succeed.
I should add that un-countered offensive order-reversal doesn't alwlays
succeed in wv, NES, DSV, or SMA either. Sometimes it works, sometimes it
doesn't, depending on the faction-size numbers.
In those methods, defensive truncation makes it impossible for offensive
order-reversal to succeed.
A voters Bury B, and B voters respond by truncating:
As in the last example, B>A>C>B.
Discussing Raynaud, Mike writes:
"B has the biggest pairwise defeat, 75. B is eliminated, and with just A & C
remaining, A is now the unbeaten candidate and wins.
With wv, the A voters' offensive order-reversal backfires, due to the
defensive truncation, and is therefore well-deterred."
Wv elects C, as does SCRRIRVE.
Chris shows one example in which SCRRIRVE thwarts offensive order-reversal
if defensive truncation is used. Showing one example is not the same as
demonstrating that defensive truncation always thwarts the order-reversal.
That has been demonstrated for wv, but not for SCRRIRVE.
Does SCRRIRVE have any desirable properties other than meeting CC? Who
knows, because none have been demonstrated.
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