[EM] Best IRV Tweak

Kristofer Munsterhjelm km_elmet at t-online.de
Thu Jul 8 02:41:16 PDT 2021

On 7/7/21 7:47 PM, Richard Lung wrote:
> Dear All,
> There is science and there is politics. And I believe the latter is 
> getting in the way of the former. And if the science was clearer, I also 
> believe it might open up a better prospect for the politics.

> The fatal flaw of all these "tweaks" is that they are tweaks or ad hoc 
> after-thoughts. It is that unscientific thinking which also makes the ad 
> hoc additional member system or Mixed Member Proportional, the HOW NOT 
> TO DO IT of election methods.

I agree that a method must live or die by the strength of its 
properties, and not much else. If a method appears to be intuitive but 
returns rotten winners, too bad for that method.

So why then Condorcet-IRV tweaks? Two reasons. The first is that they 
seem to be the only known methods that pass both Smith and DMTBR, which 
is useful when you want max resistance to strategy and still be 
Condorcet. And the second is that legislators used to IRV unfortunately 
impose a "must look not too different from IRV" criterion.

I'd wish that were not so, so that we could just advocate Ranked Pairs 
and be done with it. But if people are concerned about DH3 (or FairVote 
uses its possibility to say their method is better), then DMTBR it is. 
And if the politicians need simple methods - or need IRV-likes - then 
that's what we'll have to find.

But: that a method lives or dies by its properties is completely neutral 
to the origins of that method. So even a quick and dirty hack can have 
great property compliance. It's just less likely to be the case than if 
the method was properly planned ahead of time to pass the right properties.


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