[EM] Kevin: Your method has truncation strategy

MIKE OSSIPOFF nkklrp at hotmail.com
Sat Jan 3 23:50:01 PST 2004

Kevin wrote:

My remarks were about MinMax (Pairwise Opposition), which elects the
candidate who minimizes the maximum votes against him in any pairwise
contest (be it victory or defeat).

Admittedly I don't know much about offensive strategy for this method.
Burial seems potentially effective.  But truncation doesn't appear to
be a useful strategy of any kind in "MMPO."

I reply:

Defensive truncation is an effective order-reversal deterrent in MMPO, just 
as in wv Condorcet ww, and for the same reason. Here's as example. It's my 
standard 3-candidate IRV bad-example. In this example everyone's greatest 
votes-against is in a defeat, so it's the same as PC:

Silncere preferences:

40: ABC
25: BAC
35: CBA

The A voters order-reverse against B:

40: ACB
25: BAC
35: CBA

Candidates' greatest votes-against (considering all of theiri pairwise 

A: 25 + 35 = 60

B: 40 + 35 = 75

C: 40 + 25 = 65

A wins. The A voters' offensive order-reversal has succeeded in stealing the 
election for A.

Now the B voters defensively truncate:

40: ACB
25: B
35: CBA

Now C's greatest votes-against is reduced. Now it's only 40. C wins.

The A voters have worsened their result by their offensive order-reversal. 
The regret attempting it. If the B voters had announced in advance that they 
weren't going to rank a 2nd choice, or if there'd been articles and 
broadcasts, letters to the editor, or call-in calls recommending that B 
voters not rank a 2nd choice, the A voters would know better than to attempt 
the order-reversal, and B would win:

Greatest votes against when A voters truncate and B voters do not:

A: 60
B: 35
C: 65

B wins.

Mike Ossipoff

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