[maemo-community] STV voting strategy

From: Juho Laatu juho4880 at yahoo.co.uk
Date: Sat Mar 21 00:35:02 EET 2009

Few comments of STV methods and strategies (an area that I'm interested in also outside this community).

Dave Neary wrote:

> There is another way to count, which only makes sense with
> electronic
> counting (and is thus harder to verify), and that's
> fractional transfers.

Yes, fractional transfers are a fair way to transfer the excess votes.

> In STV, you are voting primarily to
> elect your
> preferred candidate and ordering is very important. We do
> not run the
> election with a pairwise run-off system like Condorcet
> (which isn't
> suitable to multi-seat constituencies, and which is very
> hard to
> understand).

STV methods are good proportional and quite strategy free methods that are particularly suited for electing a group of independent individuals (= no party structure assumed).

There are also Condorcet based multi-winner methods (e.g. CPO-STV, Schulze STV). They give good results but their problem is that they are computationally much more complex than the sequential elimination & election based STV methods.

(Some Condorcet methods (also single-winner methods) are rather complex (to understand) but not all. The basic Condorcet compliance criterion is very simple, elect the candidate that beats all others in pairwise comparison (if there is one). Single-winner Condorcet compliant methods are not computationally too complex, some even very simple and easy to understand. They are all good (compromise oriented) methods.)

Still some comments on the topic of the title, strategy in STV. There are two free riding strategies. In some situations you can benefit of ranking some unlikely winner before your true favourite. Or you can benefit of not ranking your true favourite at all. In both cases you hope that your true favourite will be elected anyway, but with the strategy you can save the power of your vote better for your later preferences. Some STV methods are more resistant against these strategies than others. These strategies are not easy to apply and I wouldn't recommend anyone to try these in the Maemo elections. Better to just sincerely rank the candidates. Parties may in some cases try centrally coordinated vote management in political elections. Google Woodall and Hylland free riding or vote management for more info.



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