[EM] Best Deterministic Ranked Preference Method?

Kevin Venzke stepjak at yahoo.fr
Wed Dec 23 08:13:09 PST 2020

Forest wanted the below posted to EM.

But Forest, the original is not BPW. BPW only cares about the first preference winner and is only for three candidates. I called your method "BTT" in my post.

I'll take a look at your new idea.


Le mercredi 23 décembre 2020 à 10:02:27 UTC−6, Forest Simmons <fsimmons at pcc.edu> a écrit : 
>Season's Greetings!

Kristofer & Kevin pointed out the non-monotonicity and identified the original version as Stensholts BPW, 
and Kevin compared it wth some related methods with various relative advantages  ... great work!

I generalized in a different direction than Kevin, and got lucky ... the mono-raise problem fixed!

Elect the alternative that (for the greatest number of ballots B) is not pairwise beaten by any of the 
alternatives that are approved on ballot B.

This version is closest to BPW when "approved" means  "ranked equal top."

It works equally well wth implicit or explicit approval.

This method always elects from Landau, i.e. the winner is always uncovered.

This property can be traded in for the FBC by simply swapping out the phrase "not pairwise beaten" for 
the phrase "not majority defeated." (a trick I learned from Kevin many years ago)

If the voters are not allowed explicit approval cutoffs, then they should be allowed equal top, or truncation 
at the very least, in order to accommodate a default cutoff. For the FBC compliant version equal top must 
be allowed.

As we have seen from past experience, the explicit approval cutoff facilitates different responses to burial 
and chicken offensives.

We can review that in another message.

Best Wishes to All!


P.S. Kristofer, please forward this to the EM list; when I do it, I always get some spam back for some 
mysterious reason.

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