[EM] Irrelevant Ballots Independent Fallback Approval (IBIFA)

[Dave Ketchum]

On Jun 17, 2010, at 8:28 PM, fsimmons at pcc.edu wrote:
> Chris,
>
> I like this method.  It accomplishes more simply what I was trying  
> to do with some of my DSV approval
> methods:
>
> Voters can approve good candidates with less risk for regret,  
> because if their lower approvals wreck an
> approval victory of their favorite, the IBIFA method detects this  
> state and compensates for it.
>
> Both the three slot and four slot versions seem like definite  
> improvements over both Approval and Bucklin
> without sacrificing the FBC, definitely worth testing and examining  
> in more depth.
>
> Forest
>
>
> ----- Original Message -----
> From: Chris Benham
> Date: Wednesday, June 16, 2010 10:27 am
> Subject: Irrelevant Ballots Independent Fallback Approval (IBIFA)
> To: EM
> Cc: Kevin Venzke
>
... ignoring ratings
>>
>> It can also be adapted for use with ranked ballots:
>>
>>
>> *Voters rank the candidates, beginning with those they most
>> prefer. Equal-ranking and truncation
>> are allowed.
>>
>> Ranking above at least one other candidate is interpreted as  
>> Approval.

So, if I bullet vote, my one ranked candidate is disapproved as  
Bottom!!!

Leaves me still liking Condorcet, which is less into ranking patterns  
(only considers pairs of candidates from a ballot, comparing the  
rankings within each pair).

Dave Ketchum
>
>>
>> The ballots are interpreted as multi-slot ratings ballots thus:
>> An approved candidate ranked below zero other candidates is
>> interpreted as Top-Rated.
>> An approved candidate ranked below one other candidate is
>> interpreted as being in the second-highest
>> ratings slot.
>> An approved candidate ranked below two other candidates is
>> interpreted as being in the third-highest
>> ratings slot (even if this means the second-highest ratings slot
>> is left empty).
>> An approved candidate ranked below three other candidates is
>> interpreted as being in the fourth-highest
>> ratings slot (even if this means that a higher ratings slot is
>> left empty).
>>
>> And so on.
>>
>>
>> Say we label these ratings slot from the top A B C D etc.
>> A candidate X's A score is the number of ballots on which it is
>> A rated.
>> A candidate X's A+B score is the number of ballots on which it
>> is rated A or B.
>> A candidate X's A+B+C score is the number of ballots on which it
>> is rated A or B or C.
>> And so on.
>>
>>
>> If any candidate X has an A score that is greater than any
>> other candidate's approval score on ballots
>> that don't A-rate X, then elect the X with the greatest A score.
>>
>> Otherwise, if any candidate X has an A+B score that is greater
>> than any other candidate's approval score
>> on ballots that don't A-rate of B-rate X, then elect the X with
>> the greatest A+B score.
>>
>> And so on as in the versions that use a fixed number of ratings
>> slots, if necessary electing the most
>> approved candidate.*
>>
>> This is analogous with ER-Bucklin(whole) on ranked ballots:
>> http://wiki.electorama.com/wiki/ER-Bucklin
>>
>> Chris Benham