[EM] STV and weighted positional methods

[Chris Benham]

Raph Frank wrote (1 Feb 2009):

"PR-STV is designed to be similar to a process you could follow in a
town meeting like situation.

1) Each voter votes for 1 candidate
2) Work out the Droop quota
3) If any candidate exceeds the quota, that candidate is appointed to
the committee
-- Select some of the voters (equal to the surplus) who voted for the
candidate and allow them to move their vote
(This selection could be made at random, or by deweighting all of
those people's votes)
4) If no candidate reached the quota, eliminate the candidate with the
fewest votes
-- Allow those voters to move their vote to other candidates"

A simpler and more intuitive way of looking at it is that it aims to simulate an election
among school-children in which children vote by standing behind their preferred candidate
with their being  some time during which voters can change their mind and vote for a different
candidate. At the end of the process the  N candidates with the greatest number of  voters
standing behind him/her wins.

Each voter has one vote they can do what they like with. The idea is that strategic voters with 
more than just a first preference will abandon candidates they can see have no hope of being 
elected, and  (in the multi-winner version) candidates they can see are assured of being elected
without their help. At the end of the process any candidate with more than a Droop quota is
assured of being elected (without anyone needing to know what a "Droop quota" is.)

STV tries to simulate that in a regular way that is hopefully  deterministic (as in most versions), 
and guarantees all voters Later-no-Harm and of  course doesn't have the same possibilities of 
bluff and gamesmanship possible  in the live version.

At one point in history in (I think) Britain, some local councils were elected by voters writing 
their name below the candidate of their choice on a public notice-board.  This of course was 
STV-like for late voters because when they voted they could see which candidates had  no 
hope or were already assured of election. 


Chris Benham


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