[EM] Condorcet IRV Hybrid

[Forest Simmons]

On Fri, Apr 5, 2013 at 2:43 PM, Kristofer Munsterhjelm <km_elmet at lavabit.com
> wrote:

> On 04/05/2013 09:37 PM, Forest Simmons wrote:
>
>  The following observation about Condorcet IRV Hybrids has probably
>> already been made (but I have been gone for a while):
>>
>> These hybrids have no good defense against burying.  For example
>>
>> Sincere  ballots:
>>
>> 40  A>C
>> 35  B>C
>> 25  C>A
>>
>> If the A faction decides to bury C, there is nothing the C faction can
>> do about it unilaterally. They have to depend on the willingness of the
>> B faction to elevate their compromise over favorite.
>>
>
> That's strange, because one of the points of James Green-Armytage in his
> voting strategy paper was that the Condorcet-IRV hybrids were significantly
> less prone to burying than ordinary Condorcet methods. Quoting,
>
> "All Condorcet-efficient methods are vulnerable to burying, but this
> vulnerability seems to be substantially less frequent in the Condorcet-Hare
> hybrids than in most other Condorcet methods. The reason for this is that
> voters who prefer q to w will already have ranked q ahead of w, so that
> further burying w will not affect w's plurality score unless q has already
> been eliminated."
>
> ("Four Condorcet-Hare Hybrid Methods for Single-Winner Elections",
> http://www.econ.ucsb.edu/~**armytage/hybrids.pdf<http://www.econ.ucsb.edu/~armytage/hybrids.pdf>,
> p. 8)
>
> Or are we talking about different things? Perhaps C/IRV methods are less
> vulnerable to burying in the first place, but when they are, it's harder to
> employ defensive strategy to correct the burial?
>
> -
>
> Also, I seem to recall that Uncovered,X is generally more susceptible to
> burial than is X for various types of X, unless X is already rather
> susceptible to burial. It might be interesting to run a JGA type analysis
> on your "eliminate until covering" method, and compare to the Smith-IRV
> methods.
>
> The method I proposed is not of the type "Uncovered X."  The first
candidate to cover the remaining candidates may well be a covered candidate
herself.
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