[EM] Re: Runoff vs IRV

[Chris Benham]

  Mike,
I  previously wrote (Th.Jun.3)

For the purposes of comparing election methods (in a rational way that  tries that at least 
tries to be scientific)we have a long list of  technical criteria. Reasonable debate can arise 
because one method will  meet some crititerion (or criteria) that the other does not, and then 
the question is open as to which criterion is more important than the other. In the case of the 
comparison between  IRV and (Top-2) Runoff (TTR), this is definitely NOT  the case (except  for 
your  "CW  wins if one of the first-preference top two" criterion, which I've never seen mentioned 
by anyone else in any other context).

To which you replied(Th.Jun.3):

>Are you sure that I defined that as a criterion? Or did I just mention it as 
>a difference between Runoff & IRV?
>
No, you didn't cast it  as a formal , capital C, technical  "Criterion". 
 That is fine by me.  So that means that, in terms of recognised
technical criteria, Top-Two Runoff  (TTR) has NO advantage over IRV.
What is the point of having a vast array of technical criteria, if in 
the rare two-method comparison in which one completely dominates
the other (in terms of criterion compliances/failures) you scratch your 
head and say "its a matter of opinion"?

I continued:

This is because the two methods are the same when there are three candidates, and all of  IRV's 
failings are possible with only three candidates, and yet  IRV complies with criteria that  
Runoff doesn't.
IRV  complies with the criterion that some call  "Mutual Majority" and Woodall calls "Majority" 
(aka "majority for solid coalitions")which TTR fails.IRV complies with Independence of  Clones, 
which TTR fails.
<snip>
Of course when comparing any two methods that are both less than perfect, it is always possible 
to contrive some example in which one seems to give a better result than the other.

You replied:



>No, as I said before, my IRV failure examples that you're refering to are 
>not contrived. A voter-median candidate who is one of the top-2 favorites 
>isn't at all implausible, unlikely, or atypical.
>
Thats right, your example is contrived to appear semi-plausible.  I 
 think we are employing different definitions of  the word "contrived".
The example was made-up by you  (or someone)  for the (probably sole) 
purpose of putting  IRV in a bad light. If your example is so
"typical" and  "likely", then you should have plenty of evidence from 
both computer-simulations and real-life elections.

67: ABCDE
73: BACDE
100: CDBEA
84: DECBA
70: EDCBA

To the extent that your example is plausible, I don't think it is really all that damning; because 
AB and DE are solid coalitions, and A and E are irrelevant alternatives. If A and E hadn't stood, 
then C would have been first-preference last.  C's first-preference win is just an artifice of the
C faction having only one candidate, while the the other two factions each have two.

You wrote:


>But you're too quick to assume that the Republican and the Democrat are the 
>genuine top 2 favorites in our Plurality elections. We don't know exactly 
>how many of those who vote Democrat are voting for a loathed lesser-evil, 
>but it's surely a very large percentage of the Democrat voters.
>
>That casts doubt on your claim that Runoff, compared to IRV, is more 
>preserving of the artificial 2-party-system.

How does it do that? I can't see that that makes any sense at all.

It is clear from plenty of stuff that you have put on the net over the years, that you regard IRV
as unacceptable (and far worse than Approval,which you love) and that you see it as a big part of
your mission in life to block or slow down the introduction of IRV in the US, so as to give the
movement for Approval (and other methods you like) time to catch up.Therefore, not too much speculation 
is needed to explain why you try to sow confusion on (what should be) such a no-brainer as the relative 
merits of IRV and Top-Two Runoff.


 On the subject of Woodall, he tabulates properties of many methods, a few of which are ridiculous.
He aims to show which properties are compatible with others. Each different method is a proof that
the properties it has are compatible. This is potentially very helpfull if we are ever to debate
and/or vote on criteria. Mostly disagreement will only be on relative importance, not on whether
a given criterion is desirable or not. There is no point in arguing that criterion A is more important
than criterion B if we agree that they are both desirable,and there is no problem having both.

Chris Benham





http://dictionary.reference.com/search?q=contrive

http://www.yourdictionary.com/ahd/c/c0609900.html

http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=contrive 
<http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=contrive>


>

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