[EM] IRV vs Plurality

[Jonathan Lundell]

On Jan 10, 2010, at 12:42 PM, Juho wrote:

> On Jan 10, 2010, at 10:23 PM, robert bristow-johnson wrote:
> 
>> 
>> On Jan 10, 2010, at 2:40 PM, Jonathan Lundell wrote:
>> 
>>> This is a point that bears repeating, since it doesn't seem to sink in. It's much to easy to casually assume that ballots cast under one system (in this case IRV) can be recounted under some other rule with the assumption that voters would have cast the same (or at least equivalent) ballots under that other rule.
>> 
>> but i think that it is reasonable to "casually" assume that the ranked-order ballots marked for IRV would, for the most part, be the same if the election were to be decided by Condorcet rules.  that, plus the Freedom of Information laws, allows us to say what would have happened with Condorcet rules.  the tabulation rules are different, but the ballots are the same.
> 
> I believe the voters would have voted in the same way in Condorcet. That is because they did not understand how IRV works nor how Condorcet works (or at least they didn't understand what strategic opportunities there are). They were told that in IRV you just rank the candidates sincerely, and that's what they probably did. I have not heard of any (IRV specific) strategic advices that would have been given to the voters before the election.
> 
> So I believe the votes were quite sincere rankings. In the next IRV election things might be a bit different.

If we believe that all ballots reflect sincere rankings, then of course they're all the same. And it's at least plausible that most voters will vote sincerely under IRV or Condorcet, especially when they haven't had much exposure to them.

On the other hand, to the extent that voters would employ strategies, they'd be different in the two cases. I'd hate to have to guess how many voters would employ which strategies, especially in view of the strong likelihood that some voters would employ irrational strategies. (I don't think that voters are, on the whole, very good at strategizing, and "expert" advice can be bad or deliberately misleading.)