[Election-Methods] Why monotonicity? (was: Smith +mono-add-top?)

James Gilmour jgilmour at globalnet.co.uk
Wed Jan 2 07:58:08 PST 2008

Jobst had written:
> > Also, it seems difficult to sell a method when you must admit that 
> > advancing an option X may actually reduce X's winning probability...
> >   
Steve replied:
> That doesn't seem to be a problem for the Instant Runoff campaign.  ;-)  
> Do you recall an example where it was difficult to sell a method due to 
> its non-monotonicity?

This should be no surprise because, at least in public elections with hundreds, thousands or ten-of-thousands of voters in each
electoral district, non-monotonicity cannot be exploited either by the candidates or by the voters.  It could be very different in
successive elections by IRV or STV-PR where the whole electorate was a small committee of, say, ten members  -  then it MIGHT be
possible for some voters to change their preference patterns to exploit the non-monotonicity to the benefit of their preferred
candidates.   But monotonicity is a completely irrelevant criterion so far as public elections are concerned.

James Gilmour

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