[EM] Vote Management

Olli Salmi olli.salmi at uusikaupunki.fi
Fri Apr 11 12:40:20 PDT 2003

OK, I get it, I think. If all the parties voted strictly along party 
lines, averaging votes wouldn't be necessary, right?

Olli Salmi

At 22:54 +0100 10.4.2003, James Gilmour wrote:
>Markus replied:
>>  In an STV count, a candidate can win additional votes only as long
>>  as he is neither elected nor eliminated. Therefore, when a given
>>  party wants to win as many votes as possible during the STV count,
>>  this party has to take care that its candidates are as long as
>>  possible neither elected nor eliminated. The party achieves this
>>  by "averaging" the first preferences over its candidates so that
>>  each candidate is just below the Droop Quota.
>Markus is absolutely right.  Imagine a party (party "A") that expects to get
>one-and-one-half quotas of first preferences and is popular enough to pick up
>substantial numbers of transferred preferences from supporters of 
>other parties at
>later stages in the count.  So the party is sure of winning one 
>seat, but could be
>in line for two.  The party puts up two candidates.  If most of the 
>preferences go
>to the more popular candidate, that candidate is elected immediately and the
>surplus is transferred to the running mate (assuming strong party 
>loyalty among
>the supporters).  But the small number of votes the running mate 
>then has may not
>be enough to prevent the exclusion of that candidate at an early 
>subsequent stage.
>So there is no continuing candidate of party "A" to receive any transfers when
>such transfers become available as other candidates are excluded. 
>So party "A"
>wins only one seat.
>Now suppose party "A" succeeds in persuading its supporters to 
>average their first
>preferences over the two candidates.  Neither candidate is elected on first
>preferences, but both have enough votes to keep them in the running 
>while others
>below them are successively excluded.  So both can pick up 
>transferred votes and,
>if there enough transfers, both are elected.  The parties in Northern Ireland
>certainly work hard to put this into practice where the voting 
>patterns suggest it
>will be worthwhile.

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