[EM] Proportional Representation beyond STV?

[James Gilmour]

Alex wrote|:
> I put PR systems into 3 main categories:
> 
> 1)  Fractional systems:  Generalizations of single-winner methods that
> involve marking down ballots after a candidate has been elected.  STV,
> Proportional Approval Voting, and Condorcet PR all fit into 
> this category.
> 
> 2)  Plurality systems:  SNTV, cumulative voting, limited 
> vote, etc.  Just
> give the voters N votes, specify the maximum number of votes 
> they can give
> a single candidate, and elect the top S candidates, where S 
> is the number
> of seats.
> 
> 3)  List systems.
> 
> Personally, I prefer simplicity over sophistication for 
> public elections,
> so my preference is list systems for explicitly partisan multi-winner
> races, and plurality systems for ostensibly non-partisan multi-winner
> races.  But I see virtues in fractional systems when the 
> number of winners
> is 2 or 3.

If you looked at this from the elector's perspective I think you might
propose a different taxonomy and perhaps have a different final
preference.

As an aside, I would question whether you are right to describe STV-PR
as a generalisation of a single-winner method (IRV).  Both use
transferable, preferential voting, and they share a number of defects,
but STV-PR involves an essential process (transfers of surpluses) than
cannot occur in IRV, so I suspect the two are qualitatively different.
Alternatively, IRV might be considered a special case of the use of STV,
a limiting application of STV when n=1.

Plurality systems deliver better PR than multiple-seat multiple-X vote
and single-seat systems, but they fall sufficiently far short of the
other PR systems as to left out of the count.  So I won't consider them
further here because we have many examples of the other PR systems in
practical use around the world.

The other PR systems fall into two distinct categories, from the
electors' point of view:  those with the objective of securing PR of
registered political parties and other pre-existing groups; and those
with the objective of securing PR of the voters' views as expressed in
their responses to the candidates who have offered themselves for
election.  The OUTCOME of elections by these different systems may be
similar or identical (depending on how the electors vote), but the
OBJECTIVES are always very different.  List systems all belong in the
first category.  STV-PR is the only system in the second category in use
for public elections, so far as I am aware.

For list systems, registered 'parties' are essential, where a party can
be a political party, a recognised group, or a single independent
candidate.  Voter choice is restricted - more in some systems, less in
others.

For STV-PR, registration of parties and groups is not essential (though
it is common for other reasons), and voters can choose freely among all
the candidates.  PR of political parties will be obtained (as an
outcome) if the voters vote the parties' tickets.  But PR of political
parties will not be obtained if the voters are motivated to mark their
preferences by some other priorities.  That will make the party managers
very cross (as I know from personal experience), but the voters will get
the PR of whatever it was THEY wanted.

The differences between these two categories of PR voting systems are
profound and fundamental from the electors' point of view.  The systems
create quite different relationships between the elected members and the
electors they represent.  This has major implication for what we mean by
'representation' in a representative democracy.

James