[EM] STV - the transferrable part is OK (fair), the sequential round elimination is not

[Juho]

On Nov 2, 2009, at 4:50 PM, Jonathan Lundell wrote:

> On Nov 1, 2009, at 10:51 PM, Juho wrote:
>
>> I wouldn't be as strict as saying that Droop proportionality is an  
>> absolute requirement. I'd be happy to classify all methods that  
>> approximate the principle of x% of votes means x% of seats as  
>> "acceptable PR".
>
> I'd like to see a definition of what that really means.

I don't have any exact formulation, but the idea is that one can  
deviate from the basic principle only because of rounding errors,  
moderate distortion caused by districting, maybe some generally  
accepted thresholds to party size etc. Not very exact but the meaning  
is exact, implement full proportionality except where there are valid  
(practical) reasons to (slightly) deviate from it.

>
> To harp on California again: we have 53 Congressional districts, all  
> (of course) single-seat FPTP. The distribution of Democratic and  
> Republican seats is surprisingly close to representing state party  
> registration.

Yes, FPTP in single-seat districts is statistically proportional, but  
of course it very strongly favours large parties. This is thus  
proportional in some sense but doesn't fit well in my definition above  
since deviation from full proportionality (that would allow also  
smaller groups to survive) is much larger than what would be necessary.

>
> Is this acceptable PR? I hope your answer is "of course not" (if it  
> isn't, we can have that discussion).

I note that a two-party system can be seen as one style of democracy  
that may be chosen intentionally. But if the target is to have PR then  
such single-seat FPTP systems are of course not good at all.

>
> The important thing about DPC is that it guarantees proportional  
> representation to solid coalitions. The PR isn't dependent on  
> strategic nomination or voting, on segregated or gerrymandered  
> districts, or on fortunate accident.
>
> If we didn't have DPC methods, then we'd certainly be justified in  
> finding alternative "acceptable" methods. But since we do, it seems  
> to me that alternative methods have a high bar to meet.
>
> (I'd class party lists as at least potentially meeting the DPC,  
> within whatever nomination and threshold constraints they have.)

I agree that DPC is a nice criterion. In practice I'm not that strict  
since I believe also methods that are close to DPC work quite well.  
For example basic d'Hondt with party lists may be close enough to PR  
although that method slightly favours large parties (when allocating  
the fractional seats). As already noted districting typically causes  
larger deviation from PR than the algorithm that is used within each  
district. There are many ways to implementing PR "well enough". Maybe  
in most cases there are no major strategy and fairness related  
problems although DPC was not met fully. _Approximation_ of DPC is  
however a requirement if one wants "reasonable PR".

>
>>
>> Note that even if some method strictly follows e.g. Droop  
>> proportionality there may be other factors that distort the  
>> picture. It is for example typical that the size of electoral  
>> districts causes bigger deviation from proportionality than the  
>> method that is used within each district. In the extreme case  
>> single member districts may give disproportional power to few (e.g.  
>> two) parties (even if the actual method would be proportional (like  
>> plurality in a way is for single member districts :-)). Also e.g.  
>> 10 districts of 10 seats each typically means considerable bias in  
>> proportionality in favour of the large parties.
>>
>> If the votes (and proportionality) are counted at national level  
>> that fixes the (district fragmentation related) problem. STV is at  
>> its best in small districts with small number of candidates and  
>> seats, so it typically leaves some space to distortion in  
>> proportionality as caused by the district structure. List based  
>> methods have also similar problems but in them it is easier to have  
>> the whole country as one district (=> better proportionality but  
>> weaker local representation (and as a result weaker "regional  
>> proportionality")), or they can be easily extended to count the  
>> "political proportionality" at national level but still allocate  
>> the seats in the districts (and thereby maintain also "regional  
>> proportionality" and more local representation).
>
> Certainly if we had national PR in the US (or even statewide PR in  
> the larger states), we'd have a degree of locality--STV within multi- 
> seat "superdistricts", say, or some variation of MMP.

Yes, I think STV s a quite natural step for countries that have a two- 
party history. MMP could be popular since it can offer some form of  
"single local representative". That sounds safer to voters and  
politicians that are used to the very local representatives (=one of  
the good points of FPTP) of the single-seat district style of FPTP.

Also other paths are possible in politics although in these questions  
I expect many important players to have an interest not to propose any  
radical changes. If one wants some particular solution to win (even a  
method that is not close to the existing one) a good approach might be  
to start from the not so hot environments (like schools, churches,  
clubs, student associations, towns etc.) and then expand if people  
find the new forms of democracy useful. Good Internet and media  
services are important to demonstrate the benefits and make the  
movement popular. This way it is possible that the incumbent  
politicians can not stop the train even if they would like to do that.

(Also single-seat districts + full proportionality is possible (and  
could be liked in single-seat countries) but that would mean that the  
most liked candidate would not win in all districts. There is thus a  
balance between full regional proportionality, full political  
proportionality and full fairness in selecting the individuals, and at  
least one of these criteria must yield to give space to the others.)

Juho



>
>>
>> My point thus is that proportionality should be observed at the  
>> "national level", taking into account also factors like districts  
>> and number of available candidates and parties, cutoffs,  
>> restrictions in nomination etc.
>
>