Honest vs. manipulated ratings
djmarsay at dra.hmg.gb
Tue May 12 09:30:20 PDT 1998
I consider Mike Saari's suggestions very sensible for many voting
situations. However, I think that if used in UK general elections,
the result could be significantly affected by tactical voting in many
I think that there is a consensus that a voter will probably give
maximum points to their best option, minimum to their worst. But what
about the others? To adapt Mike's example, consider 3 flavours of
pie. I would tend to rate it 'honestly'. However, if I thought that
my favourite option was unlikely to win I would tend to over-rate
the second option, to minimize the risk of the worst option winning.
Similarly, if I thought that the worst option had no chance I would
tend to under-rate the second option, to give my favourite the best
chance. Of course, I might make a mistake, but I think I'd risk it.
I think that we might try to compare Mike's method with
first-past-the-post (FPP). I think that a sensible voter will always
rate the options in an honest order, unlike FPP. This means that the
ballots will tend to record the honest order. I believe this to be
essential for any voting system. With FPP when voters vote tactically
the 'real' support for a party (e.g., centre) may be hidden. With
Mike's method the support will be documented. Voting tactically isn't
so much of an issue when the estimates of support are well founded.
I would prefer to treat the ballots as simple rankings, and to use
Suppose that there are three parties, with one a 'centre' party.
Suppose that the other parties rate the centre party as 0. Then it
could happen that a party with 60% 1st place support loses to the
centre party. (E.g., parties have support of 60, 20.1, 19.9 %). For
Condorcet, a party with a majority always wins. Although I consider
myself a moderate, I would prefer a method that respects a clear
majority. For Condorcet, there is no situation for which a majority
of the electorate would prefer a particular alternate method.
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.
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