[EM] Explaining PR

[Jonathan Lundell]

On Sep 20, 2009, at 7:49 AM, Brian Olson wrote:

> Catching up from a couple weeks ago, I just wanted to add my short- 
> short version of explaining Proportional Representation that usually  
> gets a good response from people:
>
> "A 20% group should get 20% of the seats."

Kathleen Barber has a nice line in her book A Right to Representation:

> Proportional representation is a simple principle, derived from  
> democratic theory, that in a representative body the share of seats  
> won should correspond to the share of votes won. The electoral  
> system is thus the link between the preferences of the voters and  
> the making of policy. As Ernest Naville wrote in 1865, "In a  
> democratic government the right of decision belongs to the majority,  
> but the right of representation belongs to all."



Brian's line gets at the "what" of PR; Barber and Naville take a stab  
at "why". Raph, I think, was also trying to get at "how", specifically  
for STV. They're all useful questions to ask & answer.

Tideman does a nice job, I think, in his recent book and a couple of  
earlier papers, where, in a somewhat longer form, he looks at the  
evolution of STV, beginning with the easy-to-understand method of  
Thomas Hill, and proceeding through several refinements to Meek and  
Tideman's own CPO-STV.

One thing I like about this line of explanation is that the starting  
point is easy to grasp, but it's also easy to grasp its real  
shortcomings, which makes the next refinement in turn easy to  
understand as a means of addressing one or more of the shortcomings.

Unfortunately, I don't think there's a version freely accessible  
online (though I haven't searched Google Books recently).
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