[EM] Fwd: Is Condorcet The Turkey?

[Dave Ketchum]

On Wed, 18 Jun 2003 03:47:10 +0200 (CEST) Kevin Venzke wrote:

>  --- Dave Ketchum <davek at clarityconnect.com> a écrit : 
> 
>>>(3)  Strategy concerns, not necessarily catastrophic but enough to
>>>complicate voting.  For example, under Condorcet voters have the ability
>>>to dump a low-utility Condorcet winner using a prisoner's dilemma-based
>>>strategy.  Some of us are quick to discount the possibility of voters
>>>using this type of strategy, but this phenomenon is actually quite
>>>common.  Civil society is built on individuals sacrificing to varying
>>>degrees for the common good.  We willingly forgo certain things without
>>>expecting immediate compensation, because we expect to be compensated in
>>>the "big picture".  Otherwise we'd all be out looting museums.  Or
>>>common courtesy-- take the simple act of holding a door open for a
>>>stranger carrying an armload of packages-- it's not like you expect a
>>>tip.  Rather, you expect to reap the benefits of living in a society
>>>where people hold doors open for strangers with packages.
>>
>>Please explain "prisoner's dilemma".  I do not remember any suggestion of 
>>such.
> 
> 
> http://groups.yahoo.com/group/election-methods-list/message/11387

Thank you - I had read it, and not that long ago.
> 
> "Some of us are quick to discount..." probably refers in part to me.
> 
> If people do altruistically truncate, it means that Condorcet is probably
> less likely to elect a low-utility candidate than if otherwise.  But I think
> Bart's point is that voters shouldn't have to think about this.

My reaction is that this supposed regard for others is best ignored. 
Starting with what Bart wrote May 27:
> 
> Not entirely true, although this involves a prisoner's dilemma.  
> 
> If, in advance of the election, the vote count is not known, but A and C
> are believed equally likely to win in a head-to-head contest, the A and
> C factions can agree to truncate and block B from winning, thereby
> giving A and C each a 50% chance of winning.  This increases the
> expected utility of the outcome for both A and C, if B was a likely
> winner on fully-ranked ballots.
> 
> Some believe a prisoner's dilemma strategy to be unworkable, since
> either side can "cheat" the other by failing to truncate, but the cost
> of being cheated seems low in this case.  If nothing else, it seems like
> a bit of a dilemma to decide how to play the prisoner's dilemma.

Bart is saying:
      Starting with: 49 ABC, 2 BAC, and 47 CBA (estimating a near tie).
      A and C backers could agree to lock out B by truncating to A and C.
      Then each worries about whether they can expect the other to truncate.

In this case I like better acting on regard for SELF:
      Starting with: 49 ABC, 2 BAC, and 47 CBA
      Translation:  A and C backers each PREFER B over their major enemy.
      A and C backers hear something UGLY about B
      Selfish response is: 49 ACB, 2 BAC, and 47 CAB
      No value in a fragile agreement.  Or, if B remains attractive to 
some As and/or Cs, why would they join the proposed agreement - or honor 
it even if they agreed ahead of time?

Seems to me the words about expected utility are misleading.  A and C 
backers obviously rank their preference first.  They properly go next for 
whichever remaining candidate is their preference among such.

Also seems to me that "low-utility candidate" gets misused:
      ABC says that this voter assigns most utility to A and something 
less - perhaps negative - to C.  Voter has placed B between - PERHAPS 
almost as positive as A; PERHAPS almost as negative as C.
      Looking at the initial estimates above, A and C could perhaps be 
rated as low-utility with some voters rating A or C as high-utility and 
others giving each the opposite rating.  B could possibly be rated as 
moderate-utility, for noone has assigned B last choice.
> 
> Kevin Venzke
> stepjak at yahoo.fr
-- 
davek at clarityconnect.com  http://www.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
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