[EM] New 3-slot FBC method

[Dave Ketchum]

Why bother?

Looks much like IRv, but seems yo avoid my complaint against IRV.

Has IRV's problem that patterns from each precinct must be sent to 
district (I like Condorcet for producing an array that can be totaled for 
precinct, subdistrict or district, and published wherever useful).

While slightly into ranking, its 3 ranks give voters headaches as to how 
to take advantage of this.

DWK

On Mon, 15 Jan 2007 08:14:29 +1030 Chris Benham wrote:
> I have an idea for a new 3-slot method, and if people like it I'm open 
> to suggestions for a name.
> (It  is similar to and partly inspired by Douglas Woodall's  "ApAV" method.)
> 
> 
>>1. Voters give each candidate a top rating , a middle rating or no 
>>rating.
>>
>>2. Fix the winning threshold T at 50% of the total valid ballots. Give 
>>each candidate a score equal to
>>the number of ballots on which it is top-rated. If the candidate X 
>>with the highest score has a score
>>equal or greater than  T, elect  X.
>>
>>3. If not, eliminate the (remaining) candidate which is given a top or 
>>middle rating on the fewest ballots, and
>>on ballots that now top-rate none of the remaining candidates promote 
>>all the middle-rated candidates to "top-rated"
>>and accordingly amend the scores.
>>
>>4. Again, if the now highest scoring candidate X has a score of at 
>>least T then elect X. (T does not shrink
>>as ballots 'exhaust').
>>
>>5. Repeat steps 3 and 4 until there is a winner. If  no candidate ever 
>>reaches a score of T, elect the candidate
>>that is top or middle rated on the most ballots (i.e. the Approval 
>>winner).
> 
> 
> 
> Note that in the course of the count no candidates are ever "demoted" on 
> any ballots from middle-rated to
> unrated. Both the winning threshold and the elimination order is fixed 
> at the start and don't change.
> 
> I think this is now my favourite method that meets FBC/SF. I have it 
> meeting this and Mono-raise and 3-slot Majority
> for Solid Coalitions, and Plurality and  Minimal Defense.
> 
> Comparing it with MCA and ER-Bucklin(Whole)  it seems to have a less 
> severe LNHarm problem and no disadvantages
> that I can see except that is slightly more complicated than MCA.
> 
> Also it has several advantages over "Majoritarian Top Ratings"(MTR).  It 
> doesn't have as bad a Clone-Winner problem.
> 
> 25: A>B
> 23: B>A
> 45: C
> 07: D
> 
> MTR elects C here while my suggested method ("majoritarian disapproval 
> elimination"? MDE) elects A.  B is a clone of
> A, and if  B is dropped from the ballots then both methods elect A.
> 
> MDE  probably fails Condorcet(Gross), but doesn't as easily fail  
> Condorcet Loser.
> 
> 5:A>B
> 5:B>C
> 5:C>A
> 3:D>A
> 3:D>B
> 3:D>C
> 
> Here MTR elects the Condorcet Loser and  Approval Loser D. I think MDE 
> can only elect a Condorcet loser who
> is the Approval winner.
> 
> Also in MTR zero-info. voters  with one big sincere ratings gap (so they 
> are chiefly concerned that any one of the acceptable/good
> candidates defeats all the unacceptable/bad candidates) have the weird 
> incentive to randomly middle-rate half the unacceptable
> candidates in the hope of artificially handing out some 
> majority-strength defeats. In MDE those voters should simply not middle-rate
> any of the candidates (certainly none of the Unacceptables).
> 
> MTR has a saleability problem in that it uses a pairwise mechanism as 
> part of its algorithm (MDD), but then fails both Condorcet and
> Condorcet Loser . I think MDE's algorithm is more natural and more 
> appealing to say "IRV supporters".
> 
> I'm interested in any comments or corrections.
> 
> Chris Benham
-- 
  davek at clarityconnect.com    people.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
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