[EM] Proportional multi-winner ranked voting methods - guidelines?

[Armando]

Hello,
I am a new subscriber, and I am not an expert.

I am looking for multi-winner election with fair proportional representation. 
I would like to find a method allowing voters to vote “transversally” through parties: it could decrease conflicts.
I would very appreciate if you can help me giving “guidelines”, explaining pros and cons, advising further readings. I thank you very much in advance.

I would like to open two issue:

1. Best multi-winner ranked method for a PROPORTIONAL ASSEMBLY

I read of CIVS <http://civs.cs.cornell.edu/proportional.html> and Schulze-STV <https://en.wikipedia.org/wiki/Schulze_STV>, and I thought they where the best for my case.
They seems better then “traditional” STV since they satisfy more criteria, with less strategic vote risk.
However I don’t understand differences among various condorcet’s multi-winner systems.

I knew also De Borda-based multiwinner systems: http://www.deborda.org/faq/ <http://www.deborda.org/faq/>
It seems De Borda got popular in the spanish party of Podemos recently: but they used a non-proportional De Borda to elect their national assembly (with DesBorda <https://vistalegre2.podemos.info/la-asamblea/#Sistema_de_votacion> by Echenique).
Others in the same party proposed (failing) the Dowdall variant <https://forms.podemos.info/wp-content/uploads/gravity_forms/247-6edda8669dd26a992ea894158e3e3d91/2016/12/PropuestaPodemosEnMovimiento.pdf>  of De Borda (it is used in Nauru’s elections too). It seems it would have been more proportional (here a simulation <http://www.eldiario.es/politica/datos-cocina-votaciones-Podemos_0_612089572.html?utm_content=buffer93f9f&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer>, 3rd figure, compare Sistema utilizado (DesBorda) with Propuesta de Anticapitalista (Dowdall-Borda)).

However De Borda Institute recommends Quota Borda System http://www.deborda.org/faq/voting-systems/what-is-the-quota-borda-system-qbs.html <http://www.deborda.org/faq/voting-systems/what-is-the-quota-borda-system-qbs.html> 

Actually I think there are few differences, for voters, between a condorcet and a borda ballot (always numbering candidates). Is it?
But what are the difference in results, considering the proportional variants?

Do you think PR-open list system helps more the more “conflictual” candidates (as could be the leader of each party, since they are overexposed to party electors “love” and to opposers “hate”)?

2. Best multi-winner ranked method for a PROPORTIONAL MIXED-PARTIES GOVERNMENT
I was fascinated by De Borda Institute’s idea: a system to elect directly a mixed government, where voters choose candidates AND best offices for them.
They call it Matrix Vote http://www.deborda.org/faq/voting-systems/what-is-the-matrix-vote.html <http://www.deborda.org/faq/voting-systems/what-is-the-matrix-vote.html> 

Could be possible to reach this purpose also with other systems, for example Schulze-stv?


Best regards,
Thank you in advance

Armando Pitocco
 


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