[EM] Example of constrained STV

[S Sosnick]

In Jun-2010, Britain's parliament used STV with two constraints to elect 3
deputy speakers.  

One constraint was that 2 of the 3 winners must be Labour MPs.  

The other constraint was that at least one of the 3 winners must be a woman.
							
Both constraints were implemented.  

One at a time, 3 trailing candidates, including the lone Conservative
female (McIntosh), were eliminated and their votes transferred to
continuing candidates.  

Then a Conservative male (Evans) was elected and his surplus transferred to
continuing candidates.  

Then, in order to save a seat for a woman and a seat for a Labour MP, two
Conservative males were excluded and their votes transferred.  

Then a Labour male was eliminated and his votes transferred.  

Then a Labour male (Hoyle) was elected and his surplus transferred.  

That left two candidates.  One of the two (Primarolo) was elected both
because she was a Labour female and because she had the larger tally.							
[End of message]


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> Today's Topics:
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>    1. Re: proportional constraints - help needed (Jonathan Lundell)
>    2. Re: proportional constraints - help needed (Jonathan Lundell)
>    3. Re: proportional constraints - help needed (Jonathan Lundell)
>    4. Re: proportional constraints - help needed (Jonathan Lundell)
>    5. Re: proportional constraints - help needed (Jonathan Lundell)
>    6. Re: proportional constraints - help needed (Jonathan Lundell)
>    7. Re: proportional constraints - help needed (Jonathan Lundell)
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> 
> ----------------------------------------------------------------------
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> Message: 1
> Date: Tue, 5 Feb 2013 10:29:12 -0800
> From: Jonathan Lundell <jlundell at pobox.com>
> To: Peter Zbornik <pzbornik at gmail.com>
> Cc: election-methods at electorama.com
> Subject: Re: [EM] proportional constraints - help needed
> Message-ID: <AEFBB92C-0617-4838-85AB-6DB78A832A2E at pobox.com>
> Content-Type: text/plain; charset=us-ascii
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> On 5 Feb 2013, at 10:23 AM, Peter Zbornik <pzbornik at gmail.com> wrote:
> > 
> >> Why the two constraints, as opposed to a single constraint the overall
> gender distribution must be 3:2 or 2:3? Constraints are hard enough (OK,
> impossible in the general case) to square with proportionality without
> making them stricter than required.
> > 
> > We dont want to quote-in the women at the last places on the party
> > list, where they are practically unelectable.
> > This is how we have defined the constraints it in our statutes, so the
> > constraints 1 and 2 cannot be "simplified".
> 
> You'd still be better off with a single constraint for the STV count, and
> then raising one candidate if required. So if the count results in two
> women ranked 1-2, raise the highest-ranked man to position #2, moving other
> candidates down as needed. In your case, at most one such move will be
> required.
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