Honest vs. manipulated ratings

David Marsay 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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