[EM] Instant Runoff Voting 3-candidate elections - pathologies considerably more common than you may have thought

[robert bristow-johnson]

On Aug 27, 2010, at 4:15 PM, Jonathan Lundell wrote:

> On Aug 27, 2010, at 12:48 PM, robert bristow-johnson wrote:
>>
>> with Score and Approval, it's easy to mark your favorite candidate  
>> (Score=99 or Approval=1).  and we know that Satan gets Score=0 or  
>> Approval=0.  then what do you do with other candidates that you  
>> might think are better than Satan?  that question has never been  
>> answered by Clay.  and any answer must be of a strategic nature.
>
> That is, to my mind, a fundamental problem with cardinal-rating  
> systems--approval, borda, range, etc. Except for some trivial cases  
> (notably two-candidate elections), the voting act is necessarily a  
> strategic exercise.

in my opinion, if you can break down a multi-candidate election into  
two-candidate elections where the end result would not be different  
(the Condorcet winner would be elected) then i think you've gotten  
past the burden of strategic voting.

in my opinion, when Candidate A is preferred by a majority of voters  
to Candidate B, then, if Candidate B is elected, some kind of anomaly  
or pathology (that might encourage one to vote strategically in the  
future).

> With an ordinal method (IRV, Condorcet (though one could, I suppose,  
> specify a non-ordinal cycle breaker), Bucklin) it's at least  
> possible (and usually a good idea) to cast a sincere ballot.

i just think that the strategy of swinging an election from the  
Condorcet winner into a cycle is just a risky strategy.  you never  
know who will come out on top; your worst enemy might just as well as  
the centrist may or as well as your candidate.  with something like  
Schulz (or Ranked Pairs which does not result in a different candidate  
with a Smith set of 3, and bigger than 3 seems to me even more  
unlikely than that of getting a cycle anyway), you are emphasizing  
more decisive elections in settling the ambiguity of a cycle.

say Ranked Pairs was the law, what kind of realistic strategizing can  
a party or group of candidate supporters do? that example of tossing a  
close election between RC (for radical center) and M (the centrist  
candidate who is also the Condorcet winner if sincere ballots are  
cast) is, in my opinion, too contrived to be a secure strategic  
guidance.  any strategy that can just as well backfire, is no strategy.

> Why the latter is a good thing is a separate discussion...


why casting a sincere ballot is a good thing or not?  i would be  
interested in reading such a discussion.  and, maybe even, piping in.

--

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."