[Election-Methods] [Election Methhods] MCA's IIB problem fixed

Chris Benham chrisjbenham at optusnet.com.au
Mon Jan 28 07:33:44 PST 2008

In your latest post  you alluded to  MCA's failure of  Independence from 
Irrelevant Ballots (IIB):

>A nice thing about the majority requirement is that if it's assumed that
>you are going to vote, there's no way that your vote can move the majority
>from one candidate to another.
But but the bad thing about the "majority requirement" is that  choosing 
between not voting and voting
for nobody (ignoring the competitive/viable candidates) can change the 
winner by changing the majority

I suggest that MCA instead of  electing the top-ratings winner only if  
that candidate's top-ratings score
is greater than half the total number of valid ballots, it elects the 
top-ratings winner (TRW)  if  the TRW's
top-ratings score is not smaller than his/her maximum pairwise opposition.

(Here I'm referring to the FBC complying version of  MCA that uses 
3-slot ratings ballots, but this
mechanism could equally be used for the version you were discussing that 
uses hybrid FPP-approval
ballots, and also to Bucklin.)

Doesn't this fix MCA's  IIB problem at no cost (except a bit more 

Chris  Benham

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