Interesting Links for 12-06-2014

[andrewducker]

• It's Really Hard to Be a Good Guy With a Gun
  (tags: guns usa )
• Using "hero rats" to save lives by finding mines. (And the rats don't get hurt!)
  (tags: rats minesweeper )
• An Open Letter To J.K. Rowling
  (tags: jkrowling Scotland independence )
• No more IPv4 addresses in Latin America and the Caribbean
  (tags: internet ipv6 ipv4 )
• Response by Ray

Comments

[danieldwilliam]

I think any non-preferential system with regional constitutencies is going to be prone to this sort of effect. You get proportionality within the region, not necessarily across the whole chamber.

I think it’s lessened by using preferential systems but I’d need to think about the mechanics of that.

But the example above is a bit of a narrow case. If I, for example, shift the vote in all of the homogenous regions very slightly, so that A has 201 votes and D 99 (rather than 199 and 101) then A wins 18 seats, rather than 9 (45% rather than 22.5%) and D wins 2 seats rather than 11 (5% rather than 27.5%)

(Using S-L everyone still wins 10 seats each or 25%).

Unsurprisingly, if you use a whole of d’Hondtland consitutuency the results are much more proportional, with A and B winning 13 seats (32.5%) and C and D winning 7 seats (17.5%) on vote shares of 31.8%, 31.3%, 18.7% and 18.2%. (No change using S-L).

So the choice is the classic choice about features of electoral systems. You can have more (or less) proportionality, or more (or less) community links to MP’s or more (or less) stable results but you can’t have everything. (Which many non-voting nerds seem not to believe or insist that eveyone ought to value the strengths and weaknesses of electoral systems as they do.)

[steer]

Yes, it is an arbitrary example finely balanced to show De Hondt favouring small parties. I think dh minimises the mean error between proportion of seats and proportion of votes. Got a long plane trip so might try to prove it. Can't remember the circumstances under which that is true, I think it is more obvious in Jefferson's formulation. Dh is pretty much what I would come up with I think. All systems have their flaws and any regional system you could come up with similar crazy.

[danieldwilliam]

If you fancy spending the flight on this I'd be very interested in the outcome of your cogitations.

[steer]

Hahaha... so I spent a bit of the flight on this and it turns out that D'Hondt is nearly but not quite unbiased. It looks like it's going to be but then you need to add a term to the quotient which makes it 1/2s+1 rather than 1/s+1 (where s is the number of seats). This, in fact, makes it the Sainte Lague method.

I was so convinced as well... didn't see that factor without working it all through.

My apologies.

[steer]

Bugger and no, there's still a mistake in my maths somewhere. I will keep trying.

[danieldwilliam]

Small parties nationally - they happen, in this example, to be large parties regionally.

[steer]

Incidentally a friend of mine has come up with a non pr system where your MPs vote in Westminster is related to their majority. It has interesting properties... All votes count equally, all regions get their most popular MP. Everyone I ever described it to hates it.

[danieldwilliam]

Yes - I hated it when it was described to me.

[andrewducker]

I think the issue there (and there are always issues with any system) is that you could end up with no representatives for a given party over a large area because they're excellent at coming a close second. So I might find that the nearest representative for me is 300 miles North, with a tiny majority.

[steer]

Yes, but if they come a close second then they have made the winning party ineffective. It does fall down if that party gets no elected MPs of course.

[andrewducker]

True, it would definitely knock down the others around them. You'd end up with some MPS worth only a couple of votes!