[EM] Paradoxes in Proportional Representation.

[Raph Frank]

On Mon, Nov 21, 2011 at 10:57 PM, David L Wetzell <wetzelld at gmail.com> wrote:
> 1. While all forms of PR fall short of proportionality in representation,
> the best predictor of proportionality is the number of contested seats.
>  Yet, PR with fewer seats induces more turnout than PR with a greater
> numbers of seats. So the election rule that gives us proportionality tends
> to make it so there are fewer competitive seats and less uncertainty about
> election outcomes and consequently lower voter participation.

What's a contested seat in PR?

In voter list systems, every vote matters, even though members near
the start of the list are pretty safe no matter what.

Likewise, with PR-STV, there are almost no safe seats.  You have to
maintain your quota of supporters or you don't get elected and other
members of the same party are competitors.

In both cases, getting the vote out matters, so there is an incentive
to vote.  There are no districts where you are guaranteed that a
particular candidates is going to win, so you need not bother.

> 2. Proportionality in representation does not entail proportionality in
> power and the latter is desired more than the former.

If certain party sizes have a disproportionally large power, then more
parties of that size will appear, this should give balance over time.

For example, if there is a 47, 47, 6 split of party support, then the
6 party is "king-maker".  However, that just encourages more small
parties and/or one of the large parties to have a splinter.

> 3. If both PR and single-seat elections are in use and the latter favors
> bigger parties then does PR need to be perfectly proportional or could it be
> biased somewhat in favor of smaller parties?

PR is slightly biased towards large parties due to various explicit
and implicit thresholds.

You could have one biased to small parties.  For example, you could
round upwards in a party list system.  However, that would encourage
lots of tiny parties trying to take advantage of the artificial bonus.

> If the two major
> parties, with a somewhat disproportionate amount of representation, are more
> dynamic then they'd tend to represent well the majority of the population
> and heed minorities that frame their issues respectfully.

The problem is that you are looking at PR through the lens of a 2
party system.  One of the main features of PR is normally that it
yields a multi-party system.