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

[Juho]

On Nov 2, 2009, at 1:53 PM, Raph Frank wrote:

> On Mon, Nov 2, 2009 at 6:51 AM, Juho <juho4880 at yahoo.co.uk> wrote:
>> 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.
>
> While I would agree there is a compromise between distict size and
> complexity for the voter, I don't agree that PR-STV is at its best
> with a small districts.
>
> Districts with 7+ seats seem reasonable, and give reasonable  
> proportionality.

I guess there is some practical limit to how may candidates the voters  
are willing to evaluate and rank. Districts of 7+ already offer  
reasonable proportionality (approximate quite well the x% of votes => x 
% of seats principle). Also the number of candidates should be small  
enough in this case so that the voters need not rank too many  
candidates (e.g. 10 candidates from each party).

The targets may be different in different places though. Finland has  
found its smallest districts of size 6 to be unacceptable (people have  
moved away from those regions and therefore the sizes have gone down)  
and plans a reform (largest district = 34 seats). Small parties can  
not currently get any seats in those small districts (they may however  
try by joining in larger alliances). The new proposal aims at (close  
to) full proportionality counted at country level.

Also the number of districts has an impact here. If there are e.g. 10  
districts of size 7 there could be a party with 10% support and no  
seats although from a nation wide perspective 10% of the votes would  
justify 7 seats.

>
>> 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"))
>
> I think they also suffer from the same trade-off, between giving
> voters max choice and preventing them being overloaded with options.
>
> Under a tree system, you still need to list all the candidates in the
> country.  However, granted the voter just needs to pick one candidate
> to vote for.

Yes, districts with independent elections set similar limitations in  
all systems. In list based systems it is just somewhat easier to  
extend them e.g. so that proportionality will be counted at country  
level. Candidate lists could still be regional if one so wants (the  
summed up votes would determine proportions at the country level, and  
seats could then be propagated back down (as in the Finnish proposal)).

>
>> 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).
>
> I think this is reasonable.  I made a suggestion about how to allow
> that while retaining the spirit of PR-STV locally.
>
> http://www.mail-archive.com/election-methods@lists.electorama.com/msg04272.html
>
> This gives allows candidate level elections locally while allowing any
> wasted votes to be distributed to parties nationally.

Yes, this is one way to extend STV to offer better proportionality at  
the country level. This method seems to combine some list type  
features with STV voting.

(Btw, did you consider the possibility of parties running their most  
popular candidates (that will be elected in any case) outside the  
party list. Is that a valid strategy in this method?)

Juho