[EM] Why I think IRV isn't a serious alternative 2

[Abd ul-Rahman Lomax]

At 03:41 AM 12/25/2008, Kristofer Munsterhjelm wrote:

>>>That's kinda contrived, but if either A or B wins, there'll be big trouble.
>>Doesn't this depend on how good Compromise is?  It is impossible to tell
>>just from the above.
>
>I was considering an unstable nation where the A and B groups want 
>to destroy each other. Even if the compromise is a near standstill, 
>it's better than having a war.

That's right. Methods which fail to find a serious compromise winner 
can have disastrous consequences. We imagine in the U.S. that "It 
Can't Happen Here," but we don't know what changes the future will 
bring. Given that there are better methods which are easier to 
canvass than IRV -- why not go for a better method now? When the 
situation arises, if it arises, that Center Squeeze is literally 
killer, it may be too late.

>Still, your point is taken. The problem with ordinal methods is that 
>you can't specify strength; but that's also, in some sense, an 
>advantage, since that means the method is less prone to being 
>tricked by noise or by optimization. Which matters more is a 
>question of perspective and what you want out of the method.

Sure. However, Range methods are actually less vulnerable to being 
tricked by noise. Range votes are sincere votes, in what they express 
as to ranking. Equal ranking is an important option, when equal 
ranking isn't an option, then low-preference votes get just as much 
strength as high preference ones. That's noise, and it can be severe. 
Those decisions may be made last-minute based on sound bites on last 
might's TV broadcast, an automated phone call received, etc. These 
phenomena don't generally shift heavy preference, but they will shift 
minor preference.

In Range, it's possible that the effect is damped, negative 
publicity, not well-considered, may lower ratings some but it would 
have to be pretty bad to shift it from 100% to 0%.

Methods which allow equal ranking devolve to Approval, which is a 
Range method, when voters fully truncate.

Optimization and the similar normalization -- the latter being 
probably almost universal -- do distort Range results, but only 
toward Approval results. Which distort towards Plurality in the 
extreme. We fix that with runoffs! Those extremes won't happen, 
apparently, and it seems that even a few voters voting intermediate 
ratings in Range can beneficially affect the result, can make it even 
better than either purely strategic ("Approval") Range or fully 
accurate representation of preference strength Range. More work needs 
to be done in the simulations.