[EM] What is the ideal election method for sincere voters?

[Scott Ritchie]

On Wed, 2007-03-07 at 13:41 -0500, Abd ul-Rahman Lomax wrote:
> I didn't answer part of the question.
> 
> At 08:20 PM 3/6/2007, David Cary wrote:
> 
> >-What exactly is a sincere Range voter?
> >How does a sincere Range voter vote and based on what?
> >Ditto both questions for Approval voting?
> 
> I answered for Range but not for Approval.
> 
> Approval is a Range method voted .... Approval style!
> 
> Sincere votes under Approval would be any vote that does not reverse 
> preferences.
> 
> If we consider the underlying preferences and ratings to be 
> expressable in Range, then we can consider that the sincere voter 
> sets -- or can be seen as setting -- an Approval cutoff rating, and 
> all candidates rated above that level are approved and all below it 
> are not. Essentially, the voter has divided the candidates into two 
> sets, and the vote is sincere if every candidate in the approved set 
> is preferred to every candidate in the disapproved set.
> 
> There is no known good reason for voting insincerely under Approval. 
> It is never forced.

This definition bothers me a bit.  We tend to think of "sincere" votes
as non-strategic, but the method you just described for "voting
sincerely" can involve a whole lot of strategy based around resizing the
sets and setting the approval threshold.

Suppose I think Bush is about 2% better than Kerry, and also think both
Bush and Kerry are a thousand times better than Nader.  Knowing what I
do about how close the election is between Bush and Kerry, I'll set my
threshold for approval very very tight, only marking Bush.  Meanwhile,
someone who thinks Nader is 2% better than Kerry, but both are way
better than Bush, would approve of both Nader and Kerry.

If we were both using the SAME metric for approval (or had no
information about how others are voting), then we'd have to vote the
same way - either very tightly and only approving our top preference, or
somewhat less stringently approving our top two.

We're not doing that though.  We're both acting very strategically here
based on information about other voters to influence the election
outcome, and at least one of us is changing our vote as a result.  That
fits just about any reasonable definition of "strategic voting" yet
you're calling us both sincere.

Thanks,
Scott Ritchie