[EM] MCA cut off points arbitrary?

Gervase Lam gervase at group.force9.co.uk
Wed Feb 26 15:40:10 PST 2003

> You gave this example:
> >51 ABC
> >49 BCA

> I'm not sure where you're going with this Cardinal Ratings analogy.

> Alex

I was trying to make a comment about the fairness of MCA.  A political 
commentator or even a politician might say that B should have won because 
B has virtually 50% of the top votes but no bottom votes.  Meanwhile, 
though A has about 50% of the top votes, this is opposed by almost 50% of 
the bottom votes.

B's mean average is higher than A's.  In other words, B would win in a 
Cardinal Ratings race.

Somebody on this list (Forest?) made a comment that a high resolution 
Sincere Cardinal Ratings would be a good and fair system.  This would be 
better than Condorcet.

Also, each voter's Sincere Cardinal Ratings can be obtained very easily 
from each voter's Utilities.  How can a voter's Utilities be "transferred" 
on to an MCA ballot for more than three candidates?

However, in practice, people would vote using the extremes of the Cardinal 
Ratings range.  Also, mentioned a couple years back on this list, humans 
seem to have a 2.5 bit resolution when grading things.  Cardinal Ratings 
isn't practical.

Nevertheless, could MCA be tweaked a very tiny amount to get closer to
the better fairness that Cardinal Ratings can give?  May be this could be 
done by having a different "Preferred" cut-off point.  Using an example, I 
suggested 2/3 of the votes instead of 1/2 of the votes.

Or should MCA be seen as an Approval race, like what I mentioned early on 
in my original post:

> MCA has Favored, Compromise and Unapproved [voting levels].
>  If the Compromise level were removed, all that would remain is Favored
> and Unapproved.  In other words, just ordinary Approval.

...and therefore a cut-off point of 1/2 of the votes is more justified.

Hmmm.  I must admit, I see a slight flaw in this.  May be I should have 
said "If the Compromise AND Unapproved were removed."

On an MCA ballot, the minimum that is required is Favored and Compromise.  
If none of those is chosen, then it could be assumed to be a vote of 

However, having all three on the ballot and asking the voter just to 
choose only one level makes it extremely easy for a voter to visualize the 
"order of preference" in which all of the candidates have been voted.  It 
would be immediately apparent on the marked ballot.

It also makes it extremely easy to implement deferment of a vote to the 
other voters, which Stephane has suggested for Condorcet.  To do this, all 
the voter has to do is not mark any of the three choices.


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