[EM] Preferential Party List Method Proposal

[Greg Nisbet]

All current forms of party list proportional representation have each voter
cast a vote for a single party. I say this is inadequate since a small party
can be eliminated and hence denied any representation (this is particularly
relevant if the legislature has a threshold). However, votes for a party
that doesn't have sufficient support to win any seats in the legislature are
simply wasted. Thus I propose an alternative method.

Each voter votes for as many parties as they wish in a defined order. My
vote might be democrat>green>libertarian>republican or something like that.

Anyway, first we calculate each party's "weight". Weight is calculated
simply by counting the number of times the party appears on a voter's ballot
in any position (this should be reminiscent of approval voting). Each party
also has a status "hopeful", "elected", or "disqualified".

Next, pick your favorite allocation method. D'Hondt, Sainte-Laguë, Largest
Remainder, anything else you can think of, with or without a threshold.

We then use this allocation method to determine each party's mandate if
everyone voted for their first preference. If every hopeful party has at
least one seat, then all the hopeful parties are declared elected. If at
least one hopeful party has no seats at all, the party with the lowest
weight is disqualified, its votes are redistributed, and the allocation is
done again with the new list of hopeful parties.

This method has some advantages over traditional systems. People would not
be motivated to betray their favorite party for fear that it will lack
enough support to win any seats in the legislature and hence their vote
would be wasted. This method can also be slightly modified into a cardinal
method, with a voter's first choice being defined as the highest rated party
on their ballot remaining and weight being calculated by the arithmetic mean
of a party's rating à la Range Voting. This class of voting method is
probably compatible with MMP, but I haven't yet worked out the details of
how that would work.
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