[EM] Condorcet divisor method proportional representation

[Kathy Dopp]

On Mon, Jul 4, 2011 at 11:18 AM, Kristofer Munsterhjelm
<km_elmet at lavabit.com> wrote:
> Kathy Dopp wrote:
>>
>> Thanks Kristofer.  I ignored the "all* in "all others".
>>
>> I must say then, I simply do not like the Droop quota as a criteria
>> because it elects less popular candidates favored by fewer voters
>> overall and eliminates the Condorcet winners some times. The Droop
>> quota seems to go hand in hand with IRV and STV methods.
>
> Then the question you should ask is where you want to balance
> proportionality and majoritarianism. When dealing with multiwinner
> elections, there are two objectives that work against each other. On the one
> hand, you'd want proportionality, so that variation in the electorate is
> reflected by variation in the assembly or council. That is, you'd like it to
> have members that some people like a lot. On the other, you'd want quality
> across the board, i.e. candidates that every voter can like to some extent.

The questions I would ask are:

1.  how to minimize "unhappiness" of the voters.  (perhaps this is
similar or the same as "Bayesian regret"?), and
2. how to ensure all voters' votes are always treated equally.

In your scenario 55% of people hate 50% of the winners and 45% hate
(ranked last) 50% of the winners.  If the Center and Right win, only
45% of the voters hate 50% of the winners and everyone else is happy.
Also, in your scenario, often the voters' votes are treated unequally
and only some of the 2nd choices of some voters are counted - thus
causing undesirable results  -- on the part of a majority of voters --
on occasion.

I.e. I'm looking at satisfying the most number of voters and fairness,
*and* on proportionality - but a much greater proportion of voters
avoid dissatisfaction by avoiding the Droop quota requirement and
looking at all voters' 2nd choices.

>
> This, as my simulations show, gives a tradeoff scale (on the Pareto
> frontier). At one end, the only thing that matters is that proportionality
> is accurately reproduced (consider an assembly that's elected by lot, and
> that it's large enough to be representative). At the other, the only thing
> that matters is what the electorate as a whole thinks of the council (which
> would give a majority party, even a 51% one, every single seat; or even a
> well-liked minority party every single seat, Range style).
>
> The Droop criterion pulls in the direction of proportionality. Like the
> mutual majority criterion says that a majority can control the single
> outcome in a singlewinner method, the Droop proportionality criterion says
> that, if you consider each seat to have a "majority", each "majority" (Droop
> fraction) should be able to control the winner of that seat. In doing so, it
> can go against the wishes of a larger group: it satisfies a proportion of
> the electorate to a greater extent at the cost of satisfying the whole
> electorate less on average.
>
> (As someone who thinks proportional representation is important, I think
>  the people may actually get a better result, on the whole, by PR. However,
> that kind of additional benefit arises from the dynamics, such as minor
> parties or independents checking major parties. That is quite hard to model,
> so when I mentioned "satisfying the whole electorate" above, I was referring
> to "according to the preferences the voters gave in the election".)
>
>



-- 

Kathy Dopp
http://electionmathematics.org
Town of Colonie, NY 12304
"One of the best ways to keep any conversation civil is to support the
discussion with true facts."

Fundamentals of Verifiable Elections
http://kathydopp.com/wordpress/?p=174

View some of my research on my SSRN Author page:
http://ssrn.com/author=1451051