[Election-Methods] Range Voting won't eliminate spoilers

[Juho]

On Mar 16, 2008, at 19:20 , Greg @ Somerville for IRV wrote:

> I don't believe that Range Voting will eliminate even the kind of
> spoilers that IRV does away with.

Range sure has some weaknesses.

> Consider two-candidate race between
> Bush and Gore in which 51 voters prefer Gore to Bush and 49 prefer
> Bush to Gore. Following the directions given on the RangeVoting.org
> website, voters should give a '10' to their favorite candidate and a
> '0' to their least favorite:
>
>   51 people rate Gore=10, Bush=0
>   49 people rate Bush=10, Gore=0
>   the result: Gore=510 > Bush=490 (Gore wins)
>
> Now we re-run the election with Nader in the race. When Nader enters,
> 5 people for whom Gore was their first choice switch to preferring
> Nader. Those 5 voters rate Nader a '10' and push Gore down to '5':
>
>   46 people rate Gore=10, Bush=0, Nader=0
>   49 people rate Bush=10, Gore=0, Nader=0
>   5 people rate Nader=10, Gore=5, Bush=0
>   result: Bush=490 > Gore=485 > Nader=50 (Bush wins)

One basic rule is that the best strategy for Range voters is to vote  
roughly in Approval style (=only 0 and 10 used). Your example is a  
valid concern on Range behaviour and it is quite possible that under  
some circumstances the method could pick a bad winner. The Nader  
supporters could however learn that their best strategy is to vote in  
Approval style Nader=10, Gore=10, Bush=0. This would keep Range still  
working (if all the voters can follow this Approval strategy  
recommendation).

Range may however fall again when the support of Nader grows. Or we  
could talk about the current Obama-Clinton-McCain case where the  
approximate first place support of these candidates is 25%-25%-50%.  
In this situation especially the Obama and Clinton supporters are in  
trouble since voting Obama=10, Clinton=10, McCain=0 (as above in the  
Nader example) would mean that they don't take any position at all on  
the Obama vs. Clinton question. Range thus is in trouble when there  
are two critical questions to answer (Democrat vs. Republican, and  
Obama vs. Clinton).

(The Nader case was easier since the voters could maybe quite safely  
assume that Nader will not win in any case. In the latter case there  
were three potential winners.)

Juho

> How could the 5 Nader voters suddenly have a different utility for
> Gore? In reality, the rating a voter will give to a candidate isn't
> some fixed objective measurement of their happiness with a candidate,
> but a rating relative to the options available. In short, everyone
> will naturally grades on a curve. To say that RV satisfies IIA is to
> ignore the reality that ratings will inevitably be relative.
>
> Thus, Nader would still be labeled a spoiler, because his entrance
> into a race causes some to rate Gore lower.
>
> Agree?
>
> Greg
> ----
> Election-Methods mailing list - see http://electorama.com/em for  
> list info


		
___________________________________________________________ 
All New Yahoo! Mail – Tired of Vi at gr@! come-ons? Let our SpamGuard protect you. http://uk.docs.yahoo.com/nowyoucan.html