[EM] Preferential Party-List Proportional Representation (PPLPR)

Vidar Wahlberg canidae at exent.net
Sun Nov 9 10:01:38 PST 2014

On Sun, Nov 09, 2014 at 02:57:57PM +0000, Toby Pereira wrote:
> The problem is how you want to define a proportional system. As you
> say, cardinal systems handle this better because you know how much
> support B really has, and you can allocate accordingly. But when you
> have ranks, it would go against how most people would define
> proportionality. I would say that if a certain proportion of people
> rank a certain party top, then that party should get that proportion
> of seats, subject to rounding errors.

If the definition of PR systems is that parties should receive as much
proportion of the seats as proportion of voters who rank that party at
top, then I agree, PPLPR obviously does not do that.
Interestingly, that more or less exclude every single other system than
plurality systems, with the possible exception of systems where voters
can split their vote. Even STV would not meet this definition; A
party/candidate could receive votes from later preferences and gain
representation beyond rounding errors. Using my previous example, B
could, depending on the STV implemention, win a seat in a 6-seat
election (16.7%) with only 1 of 401 votes (0.25%).

If naming PPLPR semi-proportional instead (PPLSPR) is deemed more
accurate, then that is quite fine by me. Arguably most party-list
systems are in fact semi-proportional systems.

> But is there a simple way of defining the ideology of your system?

The ideology is inspired by Condorcet methods, increase influence of
parties/candidates that the majority of the voters agree on, at the cost
of parties/candidates that the majority oppose.

Vidar Wahlberg

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