[Election-Methods] RE : Is this Condorcet method reasonable?

Kevin Venzke stepjak at yahoo.fr
Fri Nov 30 06:30:58 PST 2007


Hi Diego,

--- Diego Santos <diego.renato at gmail.com> a écrit :
> There were many discussions in this mailing list about advantages of
> winning
> votes as counterstrategy against order reversal. But sometimes truncation
> is
> risky.
>
>  Consider this example:
> 
> 46: A > B > C
> 44: C > B > A
> 10: B > A > C
> 
> B is CW.
> 
> Offensive strategy by A voters:
> 
> 46: A > C > B
> 44: C > B > A
> 10: B > A > C
> 
> A wins under RP(wv) or margins.
> 
> If truncation would be used:
> 
> 46: A > C > B
> 44: C > B > A
> 10: B
> 
> C, the sincere Condorcet loser, wins.
> 
> Winning votes induces truncation. Voters should feel free to express
> complete preferences.

I agree, they should. But how can you promise it?

> I was thinking in something similiar to "automatic truncation", i. e.,
> pairwise stregth in ranked pairs should be measured by plurality. If
> approval is used, the method becames DMC. Maybe approval cutoffs are not
> needed, then RP(plurality) is sufficient.
> 
> RP (plurality)  or pairwise sorted plurality offers weak burial
> resistance
> and is summable, opposite to Smith,IRV.

However, using the plurality vote as the strength of a defeat would cause
clone independence to be violated. More importantly, it's likely that this
measure would mean that you need to rank a viable candidate in the top
position on your ballot, or risk causing him to lose.

In my opinion it's better for it to be safer to be sincere about your first
preference, than for it to be safe to rank less preferred candidates whose
supporters you fear will use strategy against you.

Kevin Venzke


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