[EM] Majority Approval Filter (MAF) - Draft 3
dodecatheon at gmail.com
Thu Dec 13 12:25:30 PST 2018
Your proposal makes sense to me for elections with a certain amount of
consensus. However, it would be prudent to ensure that your method can
still yield a reasonable solution in the absence of clear consensus.
For example, say candidate A1 is the approval winner with 40%. There are
no candidates in the Plurality Approval or Opposition Candidate pool.
My preference in such a situation would be to include
A1, the approval winner,
A2, the approval runner-up,
B, the approval winner after excluding all ballots that approve A1, and
must have excluded approval strictly less than 40%.
If total approval for A1 and B is less than 75%, I would continue including
the approval winner on ballots that exclude A1, B, and previous
complementary opposition candidates, until the 75% threshold is met. In
the example above, A1's approval plus B's excluded approval could very
easily fall below 75%, so it would likely be necessary to include candidate
C, the candidate whose approval is highest on ballots that do not approve
of either A1 or B.
I think including A2 (even if A2 is different than B or C) is important
because with less than 50%, there isn't a strong consensus on A1.
Unfortunately this method does require a recount, but you can get A1, A2
and B with just a single summable count (accumulating the pairwise array of
votes for candidate i when candidate j is not approved), and in subsequent
counts, that pairwise array can help find both C and D if necessary.
On Sun, Dec 9, 2018 at 8:32 PM Rob Lanphier <robla at robla.net> wrote:
> Hi everyone,
> I've made some progress on the Majority Approval Filter proposal,
> which (as of December 7) I've published as "Draft 3" on electowiki;
> The current draft is more verbose, but I hope that it's clearer and
> more straightforward than the last two drafts. I've also published a
> blog post introducing latest draft on my personal blog and on
> Here's my simplified version of the explanation:
> 1. Select the candidate who receives the highest approval rating
> 2. Also add all candidates who receive greater than 50% approval
> 3. Possibly add opposition candidates if doing so is necessary to
> ensure that at least 75% of the electorate has someone they hope to
> vote for in the general election. Limit the number of candidates who
> qualify with 40%-50% approval to be less than or equal to the number
> of candidates who qualify with 50%-75% approval.
> I realize there's some handwaving in this simplified version, so I'm
> including the full text of the important bits below.
> Thanks especially to Ted Stern, but also to everyone who replied on
> the "[EM] Approval-based replacement for jungle primary" thread. I
> greatly appreciate the later replies from Kristofer Munsterhjelm and
> Richard Fobes, and I owe you two more detailed and direct replies to
> their emails now that I've published Draft 3.
> Addendum - Full definition of Majority Approval Filter (Draft 3)
> Copied from <https://electowiki.org/wiki/MAF>):
> ### Goal ###
> A set of rules for holding a primary election with an Approval
> Voting-style ballot, providing motivation for all candidates to achieve
> the highest approval rating, and resulting in a general election Ballot
> Satisfaction Score of at least 75%. The "Ballot Satisfaction Score" is
> the percentage of the electorate which approves of at least one
> candidate on a given ballot.
> ### Pools ###
> Candidates advancing to the general election must qualify for one of the
> following "Pools". Candidates that don't qualify for one of the Pools
> below are "Non-advanced Candidates". By default, all candidates are
> Non-advanced Candidates until they qualify for one of these Pools:
> - "Supermajority Candidate Pool" - all candidates who receive greater
> than 75% approval
> - "Plurality Candidate Pool" - all candidates who receive greater than
> 50% approval, but do not qualify for the Supermajority Candidate
> Pool. If no candidate receives greater than 50% approval, this pool
> will contain the leading candidate, who may have less than 50%
> - "Opposition Candidate Pool" - a subset of candidates who receive
> greater than 40% approval, but do not qualify for the Plurality
> Candidate Pool
> ### Rules ###
> Sequential steps for filling the above Pools with qualified candidates:
> 1. Select the candidate who receives the highest approval rating. This
> is the "Top Candidate" and automatically qualifies for the general
> election ballot by one of the following rules:
> - 1a. If the Top Candidate receives greater than 75% approval, add
> this candidate to the Supermajority Candidate Pool.
> - 1b. If the Top Candidate receives less than 75% approval, add
> this candidate to the Plurality Candidate Pool.
> 2. Complete the Supermajority Candidate Pool and the Plurality
> Candidate Pool using the following rules:
> - 2a. Add any Non-advanced Candidates with greater than 75%
> approval to the Supermajority Candidate Pool
> - 2b. Add any Non-advanced Candidates with less than 75% approval,
> but greater than 50% approval to the Plurality Candidate Pool
> 3. Evaluate the Ballot Satisfaction Score (defined above) using the
> following rules:
> - 3a. If the Ballot Satisfaction Score is greater than 75%,
> candidate selection is complete. Skip to step 5
> - 3b. If the Ballot Satisfaction Score is less than 75%, proceed
> to step 4.
> 4. If there is one or more candidates in the Plurality Candidate Pool,
> attempt to add an equal number qualified candidates to the
> Opposition Candidate Pool, evaluating each Non-advanced Candidate
> using the following steps
> - 4a. Find the Non-advanced Candidate with the highest approval
> - If this candidate has less than 40% approval, no further
> candidates qualify to be added to the Opposition Candidate
> Pool. Proceed to step 5.
> - If this candidate has greater than 40% approval, add this
> candidate to the Opposition Candidate Pool, then proceed to
> step 4b.
> - 4b. Compare the size of the Plurality Candidate Pool and the
> Opposition Candidate Pool
> - If the Plurality Candidate Pool has more candidates than the
> Opposition Candidate Pool, skip back to step 3.
> - If the Opposition Candidate Pool contains an equal number of
> candidates to the Plurality Candidate Pool, proceed to
> step 5.
> 5. Candidate selection is complete. Advance all candidates in the
> Supermajority Candidate Pool, the Plurality Candidate Pool, and the
> Opposition Candidate Pool to the general election.
> Election-Methods mailing list - see http://electorama.com/em for list info
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