This is a copy of a message the author posted to the Politicians and Polytopes mailing list (message 141). A constraint on voting methods of +/- 45 degrees maximum tilt deviation from First Past the Post (FPTP), is arrived at.
‘FPL’ means the ‘First Preference Loser’ rule, as illustrated by the example at the bottom which fails it. It stops a FPTP vote for a candidate making the candidate lose. The P4 rule is a rule to keep the infinitesimal power of preferential voting papers (e.g. STV papers) compliant with this idea: 0<=power<=1. That is not a genuine formula since “power” is not defined (but P4 somewhat is). The “0<=power” component is similar to monotonicity. STV and the Alternative Vote fail at both the “0” and “1” ends.