[EM] Preferential voting system where a candidate may win multiple seats

[Juho Laatu]

On 22.7.2013, at 16.43, Vidar Wahlberg wrote:

> On Sun, Jul 21, 2013 at 04:04:03PM +0300, Juho Laatu wrote:
>> Yes, it is possible and even typical that many small parties get their best results in the same district. One simple fix (and one step more complex algorithm) is to allocate full quota seats first and fractional seats only after them. This means that the results can be off only by less than one quota for each party in each region. (Also other more ideal methods can be developed.) I wonder if accuracy of one quota would be sufficient.
> 
> I may misunderstand you here, but I'm confused as of what would be the
> "fractional seats". Using Sainte-Laguë there's no quota and thus no
> fraction.

The simplest quota is Hare quota (= allVotes / allSeats). If a party gets 3.4 quotas of votes in some district, then it has three full quotas and one fractional quota of votes. In the algorithm above that would mean three certain full quota seats and one uncertain fractional seat. That approach is closer to quota style thinking than to divisor (e.g. Sainte-Laguë) style thinking, but it can be used in in divisor based methods too. The fractional seats will just be allocated using either a largest remainder method or a divisor method. With Sainte-Laguë one could use also Droop quota instead of Hare quota if one finds that more appropriate, or whatever quota is considered best (and is not too generous in the sense that it would grant too many seats).

> Is your idea to apportion seats by first using a quota (quota = votes /
> seats), then apportion the remaining seats (sequentially giving out
> seats to party A, party B, party C, ...) as described earlier in this
> thread?

Yes, in the description above the intention was to allocate the remaining seats first to the smallest party, then to the next smallest etc.

> That might produce a sensible result, I'll see if I can modify the code
> to do something like this.

I think that approach is at least quite easy to explain and justify to the voters. A full quota is something that looks pretty much like a certain seat, and quota fractions look like possible seats.

Juho


> Let me know if this is not what you meant.
> 
> 
> -- 
> Regards,
> Vidar Wahlberg
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