[EM] Truncation

[Dave Ketchum]

On Wed, 18 Sep 2002 13:23:07 -0500 Adam Tarr wrote:

> Joe Weinstein wrote:
> 
>> There is no point in invalidating or penalizing ballots of voters who 
>> have reason to lack perfect information (especially when there is a 
>> gaggle of mostly unknown candidates), or who do have (for their 
>> purposes) perfect information but are simply trying to minimize time 
>> and effort and confusion in marking their ballots.   Rather, when a 
>> given candidate has not been explicitly marked, he can still be given 
>> a default evaluation.
> 
> 
> I think virtually everyone agrees with this.  The debate is not really 
> whether we ALLOW truncation in ballots.  The debate, rather, is what 
> strategic impact truncation has in various voting systems, and what sort 
> of incentives that gives to the voter.
> 
> Recently, there has been a revival of the debate about margins-based 
> Condorcet completion methods versus winning votes-based Condorcet 
> completion methods, with an eye towards the effects of truncation on 
> each.  Specifically, there is the remarkable fact that a voter in a 
> winning votes-based Condorcet voting system can NEVER be hurt by fully 
> expressing their preferences.  There are cases where fully voting your 
> preferences can fail to help you, but it can never actually hurt you.


This is a STRONG argument for this particular method!

> 
> This is not a distinction without a difference.  In every other ranked 
> balloting method I am familiar with, the voter could potentially look at 
> the results of an election and say, "If only I (and others like me) had 
> just left some information off the bottom of our ballot, without 
> changing the order of any candidates above that point, then I could have 
> gotten a better result."  This is not the case in winning votes-based 
> Condorcet methods, and that's an incredibly powerful statement.
> 
> One of Donald Davidson's favorite criticisms of non-IRV alternative 
> voting methods is that, "your vote for your second choice can help 
> defeat your first choice." (paraphrasing).  This is simply not true in 
> winning votes-based Condorcet methods.  It is true, however, in 
> margins-based Condorcet voting, or in Borda count, or in cardinal 
> rankings, or in approval voting.  IRV itself is immune to this 
> criticism, but in IRV your first place vote can help defeat your second 
> place vote (and give the election to someone else altogether), which is 
> not really any better.


This weakness in IRV is what keeps me arguing for Condorcet.  It is 
believable that the French could have elected Chirac via IRV and have 
thought about rioting just as they did when their approach to runoffs led 
in that direction.

> 
> So winning votes-based Condorcet voting's resistance to strategic 
> truncation is essentially unparalleled in voting systems.  Blake has 
> argued that this could encourage voters who sincerely have no preference 
> among lower candidates to randomly rank those candidates on the bottom 
> of their ballot, since it can't hurt them to do so.  This is of course 
> true, but in my mind it is an extremely minor issue - we're talking 
> about candidates who are so minor that the voter doesn't care enough to 
> form any opinion on them.  If the voter is strategically aware of the 
> advantage of full ranking, they are probably savvy enough to spend a few 
> minutes reading basic candidate statements and picking some order to put 
> the candidates in.  And in the end, doesn't it make sense to reward the 
> voter who puts more information on their ballot rather than the voter 
> who puts less?


What is there to reward unless what this voter ranks low includes 
candidates who are close to winning due to other voters' preferences?
      Should not matter what voter X does about candidates who have no 
chance of winning because other candidates will certainly get ranked 
higher by many other voters.
      Should matter how voter X ranks candidates with potential to win, 
relative to each other, without regard to how X ranks these relative to 
other candidates.

> 
> There's no way to distinguish between the lazy voter and the sincerely 
> indifferent voter, or between the informed voter and the haphazard 
> voter.  But I'd rather put the haphazard voter on nearly the same ground 
> as the informed voter than penalize the informed voter vis-a-vis the 
> lazy voter.  Especially when doing otherwise gives rise to the 
> strategically lazy voter, which is a FAR more dangerous development than 
> the strategically haphazard voter.  This is not just a philosophical 
> debate; I've shown examples in recent threads where margins-based 
> Condorcet allows seemingly undemocratic results due to truncation.  I 
> haven't seen any counter-examples where winning votes comes up with the 
> undemocratic result due to its failure to penalize full preferences.
> 
>> Forest notes that the usual American academic grading system - which 
>> has the advantage of being very familiar to almost all Americans - 
>> allows the six grades A-E.  Typically,  grades A-D are degrees of 
>> definite pass, grade F is definite fail, and grade E indicates that 
>> information is incomplete to infer a definite pass or definite fail.
>>
>> Accordingly Forest proposes that if a given election is to be run so 
>> as to allow voters to use at least four grades, then a good approach 
>> would be to allow use precisely of the six academic grades, with 
>> ungraded candidates being awarded the default grade E.
>>
>> This proposal makes excellent sense.  Four levels are surely enough to 
>> distinguish substantially distinct degrees of active approval.  One 
>> level suffices to express active disapproval.
> 
> 
> At first I didn't like this idea, but its grown on me.  The simplicity 
> to the voter of ABCD(E)F voting is worth it.  The voters who are 
> interested and involved enough to actually need six distinct levels of 
> approval are the same voters who will understand that the unmarked 
> candidate will get the E grade.


This illusion of apparent simplicity is not real:
      As a student I can dream of A, and react to what I get - THIS I am 
used to.
      In a poll I can grade a question, knowing the results may be 
averaged - this is similar.
      As an involved voter I can get a headache from this opportunity. 
Easy enough to give my true preference an A; what do I do about what is 
left of Nader, Gore, Bush, Hagelin, Buchanan, etc., since I want them less 
than A, but want to do all I can to help the least of the evils (likely 
Bush or Gore) win over the rest.
      As a voter who gets a headache from the apparent opportunity 
existing, what stops me from rounding up my friends and starting a riot?

> 
> I spent some time a few months back seeing if approval-completed 
> Condorcet could be made to work using this sort of ballot, but in the 
> end I realized that the only time approval completion worked like I 
> thought it should was when the approval votes supported the sincere 
> Condorcet winner.  When the approval votes did not do so, the system 
> encouraged all sorts of strategic manipulations.  So I gave up on ACC, 
> and I now hang my hat with winning-votes based Condorcet, which seems to 
> be the system that is most resistant to strategic manipulation by a wide 
> margin.
> 
> -Adam

--------------------------------------------------

I do offer three levels under Condorcet that could be worth some thought. 
  I rank:
      Those I like, just as has been.  Count each of these toward winning 
in their pairs against all except those above - nothing new.
      NOTB to represent those I choose not to rank, treating these as has 
been done.
      The lemons, with the rottenest one last.  Count each of these toward 
losing in their pairs against all except those below - but do it as a 
negative count as to how many voters approve them.

To clarify:
      2 A ... NOTB ... Z
      some who leave both A and Z unranked
      1 Z ... NOTB ... A
      Gives A>Z net of 1 (2-1)
      Gives Z>A net of -1 (1-2)

This much ranking seems doable to me - I can identify those I like, those 
I DISlike, and happily leave the rest in the middle.

As to 1-man-one-vote I claim no violation - each voter gets the same 
opportunity.
-- 
  davek at clarityconnect.com    http://www.clarityconnect.com/webpages3/davek
   Dave Ketchum    108 Halstead Ave, Owego, NY  13827-1708    607-687-5026
              Do to no one what you would not want done to you.
                    If you want peace, work for justice.

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