[EM] Comments on Alex's 2nd Arrow posting

MIKE OSSIPOFF nkklrp at hotmail.com
Mon May 16 21:04:08 PDT 2005

Alex said:

Given that IIA is incompatible with Pareto and non-dictatorship (i.e. 
impossible for any realistic public election method)

I reply:

IIAC isn't incompatible with Pareto and non-dictatorship. Only for rank 
methods. That's only a limitation of rank methods. Plurality doesn't have 
that limitation. Neither does Approval. Arrow's impossibility theorem could 
be entitled "Arrow's Limitation of Rank Methods".

If that's important to someone then they'd like Plurality better than 
Condorcet. Mysefl, I prefer Condorcet to Plurality. So then it must be that, 
at least for some of us, Arrow's limitation of rank methods isn't important.

The above is true if IIAC can be described by my brief votes-only 
definition. If Arrow's elusive definition says something different, then of 
course there's always the possibllity that Approval and Plurality might fail 
Arrow's unposted IIAC.

Alex continues:

, from a practical perspective, IIA is a worthless criterion.

I reply:


Alex continues:

So the value of Arrow's Theorem is not simply that it proves IIA is 
impossible.  It is that he shows that:

1)  Seemingly simple properties can be impossible to satisfy, indicating 
that election methods can be subtle and complicated things
2)  Some of these subtleties can be addressed by general statements that 
transcend any particular method, meaning that election methods need not be 
studied method-by-method.  Sure, there's a place for that approach, but that 
approach can be supplemented and informed by a more general analysis.

I reply:

Fair enough. Arrow may have been first with demonstrations like that.

Mike Ossipoff

Is your PC infected? Get a FREE online computer virus scan from McAfee® 
Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963

More information about the Election-Methods mailing list