[EM] MinMax(AWP) and Participation

[fsimmons at pcc.edu]

In his last message Juho gave an example in which MinMax(wv) fails to satisfy
the weak participation criterion that Perez said was satisfied by MinMax.  I
looked up Perez' proof, and found that he made essential use of complete
rankings, in which case margins and wv give the same results.  Joho's example
involved truncations.

Investigating further I found that MinMax(AMP) [with approval determined from
ranking versus truncation] also fails Perez' weak form of participation, but it
does satisfy the following version of participation:

If additional ballots are added, the new winner must be the old one or someone
else that is approved (i.e. ranked) on at least one of the new ballots.

This is the exact form of Participation that Approval satisfies, so we can claim
that MinMax(AWP) (with approval determined by ranking versus truncation)
satisfies Participation as well as Approval does.

I do not know if Beatpath, River, or Ranked Pairs satisfies this form of
Participation.