Irrelevant Ballots Independent Fallback Approval (IBIFA)

[Chris Benham]

 "Irrelevant Ballots Independent Fallback Approval" (IBIFA) is the name I've settled on for the method I proposed
in a May 2010 EM post titled "Bucklin-like method meeting Favorite Betrayal and Irrelevant Ballots".

http://lists.electorama.com/pipermail/election-methods-electorama.com/2010-May/026479.html

In that post I wrote that it uses multi-slot ratings ballots, and defined the 4-slot version:


*Voters fill out 4-slot ratings ballots, rating each candidate as either Top, Middle1, Middle2

or Bottom. Default rating is Bottom, signifying least preferred and unapproved.
Any rating above Bottom is interpreted as Approval.
If any candidate/s X has a Top-Ratings score that is higher than any other candidate's approval
score on ballots that don't top-rate X, elect the X with the highest TR score.
Otherwise, if any candidate/s X has a Top+Middle1 score that is higher than any other candidate's
approval score on ballots that don't give X a Top or Middle1 rating, elect the X with the highest
Top+Middle1 score.
Otherwise, elect the candidate with the highest Approval score.*(Obviously other slot names are possible, such as 3 2 1 0 or  A B C D or  Top, High Middle, Low Middle, Bottom.)

The 3-slot version:


*Voters fill out 3-slot ratings ballots, rating each candidate as either Top, Middle

or Bottom. Default rating is Bottom, signifying least preferred and unapproved.
Any rating above Bottom is interpreted as Approval.
If any candidate/s X has a Top-Ratings score that is higher than any other candidate's approval
score on ballots that don't top-rate X, elect the X with the highest TR score.
Otherwise, elect the candidate with the highest Approval score.*

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.

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




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[f***@pcc.edu]

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

Post by Chris Benham
"Irrelevant Ballots Independent Fallback Approval" (IBIFA) is
the name I've settled on for the method I proposed
in a May 2010 EM post titled "Bucklin-like method meeting
Favorite Betrayal and Irrelevant Ballots".
http://lists.electorama.com/pipermail/election-methods-
electorama.com/2010-May/026479.html
In that post I wrote that it uses multi-slot ratings ballots,
*Voters fill out 4-slot ratings ballots, rating each candidate
as either Top, Middle1, Middle2

or Bottom. Default rating is Bottom, signifying least preferred

and unapproved.

Any rating above Bottom is interpreted as Approval.
If any candidate/s X has a Top-Ratings score that is higher

than any other candidate's approval

score on ballots that don't top-rate X, elect the X with the

highest TR score.

Otherwise, if any candidate/s X has a Top+Middle1 score that is

higher than any other candidate's

approval score on ballots that don't give X a Top or Middle1

rating, elect the X with the highest

Top+Middle1 score.
Otherwise, elect the candidate with the highest Approval

score.*(Obviously other slot names are possible, such as 3 2 1 0
or A B C D or Top, High Middle, Low Middle, Bottom.)
*Voters fill out 3-slot ratings ballots, rating each candidate
as either Top, Middle

or Bottom. Default rating is Bottom, signifying least preferred

and unapproved.

Any rating above Bottom is interpreted as Approval.
If any candidate/s X has a Top-Ratings score that is higher

than any other candidate's approval

score on ballots that don't top-rate X, elect the X with the

highest TR score.

Otherwise, elect the candidate with the highest Approval score.*

*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.
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.*
http://wiki.electorama.com/wiki/ER-Bucklin
Chris Benham

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[Dave Ketchum]

Post by f***@pcc.edu
Chris,
I like this method. It accomplishes more simply what I was trying
to do with some of my DSV approval
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

Post by f***@pcc.edu

Post by Chris Benham
*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

Post by f***@pcc.edu

Post by Chris Benham
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.*
http://wiki.electorama.com/wiki/ER-Bucklin
Chris Benham

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[f***@pcc.edu]

Dave,

If you bullet vote, then the candidate that you vote for is the only one that you "ranked," so it is
considered ranked above all of the other candidates. Only the truncated candidates are considered
unranked. Chris worded it this way so that if somebody ranked all of the candidates without truncating
anybody, then the lowest ranked candidate would never be approved.

----- Original Message -----
From: Dave Ketchum

Post by Dave Ketchum

Post by Chris Benham
*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

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[Dave Ketchum]

Without the puzzle sentence all that get ranked get counted. Fine
with normal truncation, which is normal for ranking. If someone
ranks the bottom those count as least liked and rarely, if ever, cause
trouble.

With the sentence but no truncation, the bottom rank gets treated as
Bottom.

With the sentence and truncation it is easy to think of the lowest
actual rank as required to be treated as bottom.

Considering possible write-ins, do they make us see truncation?

I understand Chris is considering:
| I might change "ranking above at least one other candidate" to the
simpler (and more traditional) "ranking in any position".

Dave Ketchum

Post by f***@pcc.edu
Dave,
If you bullet vote, then the candidate that you vote for is the only
one that you "ranked," so it is
considered ranked above all of the other candidates. Only the
truncated candidates are considered
unranked. Chris worded it this way so that if somebody ranked all
of the candidates without truncating
anybody, then the lowest ranked candidate would never be approved.
----- Original Message -----
From: Dave Ketchum

Post by Dave Ketchum

Post by Chris Benham
*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

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Election-Methods mailing list - see http://electorama.com/em for list info