[EM] new working paper: "Four Condorcet-Hare hybrid methods for single-winner elections"

[Jameson Quinn]

2011/2/19 Kristofer Munsterhjelm <km-elmet at broadpark.no>

> Kevin Venzke wrote:
>
>> Hi Kristofer,
>>
>> --- En date de : Sam 19.2.11, Kristofer Munsterhjelm <
>> km-elmet at broadpark.no> a écrit :
>>
>>> Some other observations: it seems that adding a Smith
>>> constraint (Smith, or Smith//) limits the vulnerability to
>>> compromising, and that having the base method satisfy LNHarm
>>> greatly limits vulnerability to burial, since the base
>>> method is then immune to burial.
>>>
>>
>> Well actually it's LNHelp that gives you immunity to burial. (DSC, QR, and
>> MMPO are vulnerable in varying ways.) And sadly it seems to me that the
>> desirability of having other voters doubt that you will express a certain
>> lower preference, mitigates the advantage of LNHarm.
>>
>> If you look at LNHelp instead you will probably start out with
>> Condorcet//Approval, which actually is one of my favorite methods due to
>> anti-burial properties. Maybe DAC is of interest too.
>>
>
> If that's the case, then LNH isn't enough. See Armytage's strategy paper,
> http://www.econ.ucsb.edu/~armytage/svn2010.pdf . In it, Bucklin is shown
> to be vulnerable to burial (e.g. page 28). This is quite strange because
> Bucklin isn't Condorcet-efficient and so could (and does) meet LNHelp
> outright.
>
> It also seems possible to bury using Bucklin. Say that your sincere
> preference is A > B > C > D, and that B wins in the second round, but if you
> could somehow keep B from winning, then A would win in the third. Then
> dishonestly burying B, say by voting A > C > D > B, would help.
>

Of course, with MCA (that is, any Bucklin method which does not mandate one
candidate per rank), you could just vote A>  >  >B (>=C>=D). So burial is
not an essential part of what's happening there, except because of the
arbitrary restriction on your definition of "Bucklin".

As far as I can tell, nobody today advocates for that old version of
Bucklin, so it's only of academic interest. MCA, on the other hand, does
have advocates, myself included.

(Note for those who missed it: I call Bucklin-like methods without overvotes
or undervotes "MCA" because that name won in a web poll. I don't think IRV
would have made the progress it has with a name like "Hare". I also follow
the poll in saying "Instant Round-Robin Voting" for Condorcet, though I say
"Pairwise Champion" for the CW.)

>
> A method that passes LNHarm doesn't have this problem, AFAIK, because later
> preferences cannot harm your earlier preferences. Your chance of having A
> win is the same whether you vote A > B > C > D or A > D > C > B.
>
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