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

David L Wetzell wetzelld at gmail.com
Thu Feb 2 20:12:15 PST 2012


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

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...

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