[EM] Sparring over AV vs IRV at Least of All Evils...

[Kevin Venzke]

Hi David,
 
I'm trying to make sense of this as an anti-Approval argument, since you say we don't want people to pursue the
center "too doggedly." Did you explain what bad consequence follows from pursuing the center doggedly, though?
I thought I understood your post as an "IRV is not so bad" argument, until I reached this line.
 
Kevin
 

De : David L Wetzell <wetzelld at gmail.com>
À : EM <election-methods at lists.electorama.com> 
Envoyé le : Jeudi 2 février 2012 22h12
Objet : [EM] Sparring over AV vs IRV at Least of All Evils...


http://www.blogger.com/comment.g?blogID=7696446405100112491&postID=7962761243854932802 

Dale Sheldon Hess has provoked me to explain my views about IRV wrt to a 1-d politics game.  

Here's what I wrote, 
DSH:"Place a party directly in the center. Now, if I can place two more parties, I can always make your centrist lose. ALWAYS. And you can't move more-centrally to do anything about it (I can actually make it so that you can still win by moving AWAY from the center; how's that for perverse incentives!)"

dlw: Ah, but in this example, the two biggest parties are in fact close to the center(as I predicted)... and so the fact that the most centrist party doesn't win is relatively small potatoes. 

And as for the 3rd party candidate winning by going way from the center, that's a curiosity due to the uniform dist'n of voter preferences. That isn't realistic...

I've played with Yee's voteline thingy. The issue is with the uncertainty as to what is the center, since it's something that's dynamic. 

That's why I downplay the import of "center squeeze". The center can't be cordoned off by anyone and so to pick a rule based on how it pins down the center is like chasing after the wind. 

With both IRV and FPP, there's pressure to move twds the center by the biggest parties, it's stronger with IRV. Thus, the de facto center ends up becoming more closely tied to the true center.

Let's say a shift in voter preferences has D and R at the 70 and 71 penny marks and G sets up shop at 35. G wd win with both FPP and IRV, but both D and R get to move again. But there are rigidities that prevent them from moving too much too fast. And so the D's move to 55 and the R's to 56. And then G still wins if it's FPP, but with IRV then R wins. 

But what if D moves and R (perhaps stuck in FPP thinking) doesn't move, so the positions are 35, 55 and 70? In that case, G would win. 
Tragedy, right? But it can be expected that the next election will change things further so that the G's must move to the right(or merge w. the Ds) and the R must move to the L or merge with the Ds. 

The moral of the story is that parties are like the people groping around in the dark in Socrates' cave. They cannot choose exactly where on the spectrum they will be. But IRV helps us to adjust and makes the outcome closer to the center than o.w. with FPP. 

If Approval Voting had been used then D would have won by moving to 64. In fact all the parties wd be strongly encouraged to beeline for whatever the center seemed to be and with a shifting center, they'd all stumble and bump together in the dark. 

Whereas, the Gs by taking a stand at 35 at least they succeed in moving things to the left or maybe they'll get lucky... 

It's not an exact science, which is what it should be. We want people to pursue the center, but not too doggedly...

Sorry if that's fuzzy, but I think that's closer to real life...

dlw 
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