[EM] Re: SCRRIRVE & my example

MIKE OSSIPOFF nkklrp at hotmail.com
Fri Jan 23 01:29:01 PST 2004

Chris said:

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 
vote sincerely:

I reply:

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 
"burying" has.

You continued:


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 reply:

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.

Chris continues:

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.

I reply:

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.

Mike Ossipoff

Learn how to choose, serve, and enjoy wine at Wine @ MSN. 

More information about the Election-Methods mailing list