I've come back to an interesting thread:
> From: Mike Ositoff <[EMAIL PROTECTED]>
> Subject: Margins Example Continued
The debate is between 'margins' and 'votes-against' in variations of
Condorcet, who does not explicitly deal with tied rankings. The
differences cited so far concern tactical voting.
I suggest that we consider tactical voting in the particular case
where one has spatial voting. This is often used in voting theory. In
the simplest case one has a left/right scale. Voters have views along
this scale, and candidates take positions along the scale. Voters, we
suppose, never rank a candidate below candidates who are 'more
extreme'.
It is well known that one cannot avoid tactical voting in the general
case. I consider 'tactical spatial voting', where the voter's
true preferences are spatial, but their declared preferences may not
be. I claim that Condorcet with the 'margins' interpretation
(e.g., see:
>From: Norman Petry <[EMAIL PROTECTED]>
>Subject: Re: Schulze Method - Simpler Definition
)
is immune to tactical spatial voting. My tentative proof relies on the
following observation:
If x <a y and y <b z (where x,y,z are candidates and a,b are the
'margins') then x < c z, where c >= min{a,b}.
The proof is done by cases, over the possible spatial relationships
between x, y and z. Incidentally, this shows that the only Condorcet
cycles one can have are indifferences.
Being able to say that 'Condorcet/margins' copes well with spatial
voting seems to me to a big plus for 'margins'. Is the same true for
'votes-against'?
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Sorry folks, but apparently I have to do this. :-(
The views expressed above are entirely those of the writer
and do not represent the views, policy or understanding of
any other person or official body.
