[EM] Round Robins

[Alex Small]

A few things.
 
First, I like the point about Instant Round Robin as a name.  I think I will start calling it that.  Naming something after a theorist is fine in academic circles, but I can't think of too many policies that are widely referred to by the name of some theorist.  So I'm cool with the more descriptive name.
 
Second, Ralph Suter wrote:
>The only problem with IRR is when there is no Condorcet winner.
>But as far as I know, elections with no CW are totally theoretical.
>For them to happen would require voters to seriously confused
>about their preferences for different candidates.
 
Not really.  As long as candidates are on a 1D scale from liberal to conservative there won't be any significant number of voters with a preference like left>right>center or right>left>center.  However, if there's a second dimension along which to evaluate candidates then it all changes.  It could be that we replace the single left-right axis with different axes for different categories of issues, and get canidates who are fiscally conservative and socially liberal, or fiscally liberal and socially conservative.  Another way this could happen is if the second axis is some issue like character or experience.  A moderate with a sleazy record could wind up being a lot of people's last choice even though he's between the liberal and conservative on the ideological spectrum.
 
Then somebody wrote:
>I'm not so sure, Jan, since many Condorcet-efficient methods do not
>require all (n-1)*n/2 pairwise comparisons to be carried out. For
>example, ROWS is Condorcet-efficient and only requires n-1 comparisons,
>which is by far less.
 
What is ROWS?
 
Finally, what rule do people use in sports to break cycles in round robin tournaments?  I'd be inclined to use that rule in public proposals for IRR, even if it should turn out that it isn't the optimal rule from a theoretical perspective.
 
 
Alex Small

		
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