Thus the idea is
• proportionality: votes are matched with candidates so that each person elected represents the same number of voters
The method involves
• transfers: the surplus of candidates who have more votes than they need, and all the votes of any candidates who are excluded, are transferred to other candidates
• preference voting: so that any transfers can follow the voter’s preferences.
This provides voter choice: you vote for individual candidates, not just parties, and can express your order of preference for all candidates, rather than being limited to just a first choice. And it provides effectiveness by minimizing wasted votes and tactical voting. You can vote for a minority candidate who is your real first preference safe in the knowledge that if they are excluded your vote will be passed on to your next choice. While if your first preference has too many votes, part of your vote will be passed on to your next choice.
Some examples - illustrating how STV works
Denis Mollison
updated 3rd February 2019
Some data sets for which full preferential voting data are available:
Scottish Council Elections 2007
(East Ayrshire and Glasgow only)
Scottish Council Elections 2012
Scottish Council Elections 2017
Three seats from the Irish election of 2002
Trustee elections for the John
Muir Trust
(examples of preferential voting allowing equal preferences)
STV scheme for the UK parliament [pdf]