[EM] Meta-criteria 6 of 9: Heuristics. #1, simplicity

[Juho]

On May 7, 2010, at 6:13 PM, Kevin Venzke wrote:

> Hi Juho,
>
> --- En date de : Ven 7.5.10, Juho <juho4880 at yahoo.co.uk> a écrit :
>> Another characteristic feature of the Schulze method is the
>> use of winning votes. My understanding is that the history
>> behind winning votes is mostly based on strategic voting
>> related concerns. Unless use of winning votes is considered
>> ideal for sincere votes, this decision means some deviation
>> from electing ideal winners wit sincere votes.
>>
>> Yet another possible factor that may influence this
>> discussion on what the basic idea behind Schulze method (and
>> other methods) is is the concept of implicit approval cutoff
>> after the ranked candidates. Some criteria and discussion on
>> what the ideal winner is do refer to the assumption that
>> voters have indicated that they support/approve those
>> candidates that they have ranked and do not support
>> candidates that they have not ranked. (Depending on the
>> ballot type and number of candidates and interpretation that
>> could mean truncation or candidates ranked equal last.) This
>> interpretation of the votes is thus not purely ranking based
>> but includes also additional information. One problem of
>> this approach is that if voters behave this way then will
>> not express their preferences on the preference between
>> those candidates that they do not like, and that could mean
>> high level of truncation and bullet voting. Implicit
>> approval argumentation usually appears together with
>> arguments on why winning votes are natural or how they
>> work.
>>
>> My understanding of the history of developments behind the
>> Schulze method is that in addition to Condorcet
>> compatibility one has aimed at summable matrix, 100%
>> independence of clones, defence against some strategic
>> voting patterns (=> winning votes), deterministic
>> decisions (best candidate elected, no lotteries, except when
>> exact ties). I don't think the interest to aim at minimum
>> number of ballots that must be eliminated (or added) has
>> been a key target, at least not the leading one. The
>> strategic concerns must have been strong if one considers
>> winning votes not to be optimal with sincere votes.
>
> *Who* must have considered winning votes to not be optimal with  
> sincere
> votes?

I don't really know what others have thought. My first approach when I  
first time thought about pairwise comparison based methods was that  
margins would be a natural and simple way to measure preference  
strengths, and I needed an explanation to why one would use wining  
votes. The argumentation that I found was related to strategic voting.

>
> Never mind that you noticed above that WV advocates tend to have a
> different conception of truncation. (Though I wouldn't call it
> disapproval; disapproval is likely, but the point is abstention.)
>
> The arguments I remember are about majorities and sincere CWs more  
> than
> about fixing strategic incentives for its own sake.

There have been arguments that the reason why margins is not good is  
its strategic vulnerabilities when compared to winning votes. (This  
means that winning votes have been considered to be better because of  
strategy related reasons. But this doesn't say anything on if someone  
finds winning votes to be ideal with sincere votes.)

>
> FPP has strategic problems beyond those found in IRV... We don't  
> conclude
> from this that FPP is better with sincere votes. We don't take  
> arguments
> about FPP's strategic problems as an admission that  
> "otherwise" (???) FPP
> was just fine.
>
> Why couldn't I say that the point of *margins* is to minimize a  
> strategic
> incentive?

There are cases where margins are less vulnerable to strategic voting  
than winning votes but I don't recall anyone saying that margins would  
have been designed with this in mind.

> Considering that you just complained about the potential
> strategic implications of the WV view of truncation.

I mentioned at least the possibility of message "truncation =  
approval" possibly leading to shorter than fully ranked votes.

>
> Schulze and WV are only not focused on minimizing the number of
> "eliminated" ballots in the narrow sense that you pick out to support
> margins. Practically the whole point of WV is to be able to ignore the
> smallest number of preferences that were actually specified, rather  
> than
> imagined.

With 100 voters opinion 40-30 means that there are 30 no-opinions or  
equal opinions. Margins seems to assume that the (from 0 to 30) no- 
opinions are either equal opinions or 50%-50% in both directions. One  
could also assume that every truncated vote and vote that contains  
equal rankings is intentionally created by the voter and therefore the  
voter intentionally wants these candidates to be considered equal.  
Winning votes seems to assume that no-opinion and equal opinion  
correspond to voting against the pairwise winner since 40-30 and 40-0  
have the same meaning.

Juho


> The main difference between Schulze and RP is a preference
> to ignore small defeats over trying to make a ranking by locking  
> larger
> defeats.
>
> Kevin Venzke
>
>
>
>
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