On Nov 8, 2009, at 8:43 PM, Raph Frank wrote:
On Sun, Nov 8, 2009 at 5:22 PM, Terry Bouricius <ter...@burlingtontelecom.net
> wrote:
A somewhat more accessible (and available online for free) analysis
of
strategic vulnerability of various methods is in this doctoral
paper by
James Green-Armytage ("Strategic voting and Strategic Nomination:
Comparing seven election methods"). He found that Range and
Approval were
just about the worst in terms of manipulability.
http://econ.ucsb.edu/graduate/PhDResearch/electionstrategy10b.pdf
His assumptions about how people vote are not very realistic.
There are many small things in the paper that can be discussed but I
think he gives a good solid basis for further discussions and
improvements to make the results more accurate from real life
modelling point of view. This is a good attempt to describe the
practical properties of various methods from a neutral scientific
point of view.
Plurality -> vote for favourite
Top 2 - run-off -> vote for favourite and then best of top 2
Alternative vote -> honest ranking
Minimax -> honest ranking
Borda -> honest ranking
Approval -> vote for better than mean
Two short comments on this one.
- One could alternatively assume that sincere voting in Approval would
already be (at least partially) based on applying the basic strategy
of trying to make a difference between the (two, three) most probable
winners. Strategic voting would mean additional strategies on top of
the basic one.
- Unfortunately the model that James Green-Armytage used was not yet
able to handle strategic nominations in Approval. I think cloning has
an impact in Approval (clones may easily harm you).
Juho
Range -> give max to favourite and min to least favourite and scale
the rest
His analysis is pretty interesting and he has created a condition for
each method that is needed for the winner to be vulnerable to loss if
a group of voters switched their vote.
In practice, people are able to handle the basics of plurality
strategy.
It would be interesting to see how approval scores with a pre-election
poll being performed. For example, each voter approves based on a
mean threshold and then use the result of that election to work out
the top-2.
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