[EM] PR favoring racial minorities

[Kristofer Munsterhjelm]

Raph Frank wrote:
> On Thu, Aug 21, 2008 at 7:23 PM, Kristofer Munsterhjelm
> <km-elmet at broadpark.no> wrote:
>> The decoy list strategy appears because it's possible to vote for a
>> different national party and regional party (constituency candidate), which
>> leads to an overhang that can be exploited to turn top-up into parallel MMP.
>>
>> A simple countermeasure is to weight the vote pairs in a way that if you got
>> what you wanted in the constituency part, your say is diminished in the list
>> part.
> 
> This isn't possible though.  Fundamentally, FPTP
> means that a candidate can get 1 full seat while only
> being supported by 1/2 a seat's worth of voters (and often
> less).
> 
> Independents make it even worse (and as you say decoy
> lists exploit this).

What I had in mind was something like this: Say there's a single-winner 
election where the plurality winner has 35% support. Then those voters 
effectively got 0.5 (+1) worth of the vote with only 0.35 mass. The 
total voting power of the entire electorate should not be altered.

Thus

pA (unscaled) = 0.35/0.5 = 0.7
pB (unscaled) = 1.3

For the sake of the example, consider the case of 1000 votes. Then the 
scaling factor is x, so that 0.7 * x * 350 + 1.3 * x * 650 = 1000. x is 
then about 0.918, so the voters for the winner now have voting power 
0.6426 and all the other voters have voting power 1.1934.

>> For a single seat election, STV would reduce to IRV. For 1000 ballots, the
>> Droop quota would be (1000/(1+1)) + 1 = 1000 * 0.5 + 1 = 501, which seems
>> right, considering a majority is 50% + 1.
> 
> It depends on how you want to look at it.  If there are 100 seats,
> then the quota is 1/101 of the votes cast.  This works out as
> 100/101 of the votes cast in each constituency (assuming equal
> turnout).
> 
> Thus unless a local candidate hit ~99% of the local vote, he
> wouldn't actually reach the (national) STV quota.

That's true, so I don't think you should compress the entire election 
into an STV election with the same quota. Instead, keep the weights 
after the local election is done, and use those weights for the national 
election.