On Wed, 20 Jul 2005 21:36:00 +0300 Juho Laatu wrote:
Hi All,
Here is one interesting margins vs. winning votes example for you to
consider. I don't remember having seen this type of scenario. But with
good probability someone has already analysed this, so please provide
some pointers if this has been discussed on the list or elsewhere.
The example is a bit more complex than it would need to be. That is
because I prefer presenting it as a real life example instead of a
theoretical extreme case. This example fits nicely within the framework
of the the US presidential elections. Few observations follow.
20 A
15 ABC
10 ACB
35 BC
20 CB
- Democrats have nominated candidate A.
- Republicans have nominated two candidates. In addition to their normal
mainstream candidate B they have nominated also a right wing candidate C.
- All voters have taken position on Democrats vs. Republicans.
- Some Democrat voters have not taken position on the Republican
internal battle between B and C.
- All Republican voters have taken position on B vs. C.
- Democrats prefer B over C.
- Republicans prefer B over C.
- B is the Condorcet winner.
- In raking based real life elections it seems to be quite common that
voters don't give full rankings. This example has only three candidates
and therefore full rankings could be quite common. But the election
could have also considerably more than three candidates, in which case
partial rankings probably would be quite common. It is probable that
ranking candidates of competing party is less common than ranking
candidates of ones own party (just like in this example).
Partial rankings ARE appropriate - you properly do not rank when you do
not know or care which of the leftovers are better.
Now, what if some of the the 20 C supporters (C>B voters) would note
the weak position of C before the election and decide to vote
strategically C>A>B.
The word "strategically" turns me off. For whatever reason, they are
switching between C>B>A (with A's position implied) and C>A>B - between B
is preferable to A to A is preferable to B.
Not surprising that B no longer wins.
Not surprising that C wins in WV - C retains its ranking while B
becomes less desirable.
Perhaps less surprising that A wins in margins - these voters were
SUCCESSFUL in controlling outcome between A and B (though they were unable
to cause C to win).
- in the case of winning votes C wins the election with 6 to 20
strategic votes (out of the 20 C>B votes)
=> quite efficient and risk free (if one has reliable opinion poll
results available) (and if others don't use other strategies)
- in the case of margins A wins the election with 11 to 20 strategic
votes (out of the 20 C>B votes)
=> not very promising as a strategy
Yours,
Juho
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Dave Ketchum 108 Halstead Ave, Owego, NY 13827-1708 607-687-5026
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