[EM] Philosophical question for IRV experts

[Kevin Venzke]

Paul,

 --- Paul Kislanko <kislanko at airmail.net> a écrit : 
> > The method you describe is interesting, though. In the single-winner
> > case, it seems equivalent to Plurality.
> 
> It is almost like plurality plus run-offs, because a team doesn't get ranked
> x until a majority vote it higher than all remaining teams.
> 
> For example, with 65 voters, suppose the first place votes are A = 31; B=25,
> C=9. There's no majority, so votes for second are added in. A=31+15=46;
> B=25+22=47; C=9+28=37. Now B leads A and both have majorities.
> 
> My question is, at this point is it better to award only 1st to A and then
> proceed to the next round, or go ahead and award 2nd to B since B also has a
> majority?

Ah, I get it. This isn't like IRV so much as Bucklin. That is definitely
an easier way to go. With IRV, in the above scenario, only the "votes for
second" of the 9 C voters would be added in. So using the table format
that you're using, it wouldn't be possible to determine the IRV winner
in this scenario, because we need to know who the 9 C voters placed second.

With Bucklin, all votes for second are added in and actually B would receive 
1st.  It's also possible to pick A as you have done, since A started
with more votes.

Douglas Woodall has suggested a method called QLTD (Quota-Limited 
Trickle-Down) which elects the one of the two which needs the smallest
percentage of its votes-for-second to reach half the votes. In this
case A needs 1.5 of its 15 new votes (10%) while B needs 7.5 of its 22
new votes (34.1%) so A would be elected.

Except for IRV, these methods all have the same properties.

> The philosophical question comes up because if there's a tie at any step,
> going to the next column can result in a "win" for the rank in question by a
> team that was not involved in the tie, and this made me think it would
> always be right to let an iteration determine only one "winner". A few uses,
> though, made me think that is less desirable than I'd thought.

In the example you attached, I would definitely rank Miami ahead of LSU,
since Miami has an earlier majority.

In general, what I would do is have 25 columns corresponding to each slot
that the voters had. For each team, shade the square in the column at
which they got a majority, so that more than one square may be shaded
per column. Then use whatever rule you've chosen to break ties among teams
receiving a majority in the same column.

It won't look as nice, but I think it will make more sense than what you
attached. For example, under column 5, three teams receive majorities.
But California and Utah are shaded under columns 6 and 7, after votes
corresponding to those ranks have also been added in. That seems to me
to be confusing and harder to explain.

I hope that is interesting or helpful.

Kevin Venzke



	

	
		
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