Voting system in a nutshell
Scots have become some of the most sophisticated voters around over the last couple of decades.
Both the UK and constituency vote at the Scottish Parliamentary elections are simple, first past the post systems.
At the Scottish Parliamentary election we also vote by party within one of eight larger regions. Each of these then returns MSPs via a system of proportional representation.
May’s local election will see us use the most complex system - the Single Transferrable Vote (STV).
Introduced in 2007, it saw a shift from single member, first past the post wards to multi-member wards.
Voters can indicate the candidates they want and in order of preference. Only their first preference counts until their candidate is elected or eliminated from the contest.
You can vote for as many or few candidates within the ward.
Each ward has a minimum number of votes that candidates must get to be elected.
When a candidate reaches the requisite number of votes, known as the quota, they are elected.
The next preferences on their ballots are then totted up and divided among the other candidates still in the race, according to how many first preference votes they received above the quota.
These are then added to the remaining candidates’ votes and the count moves on to the next stage.
Here is an example. Most local elections see a far smaller surplus of votes than suggested here).
There are three seats with a total of five candidates (red, yellow, blue, green, purple) in a ward. A total of 1000 people vote in the ward.
Each candidate must achieve a certain number of votes to be elected. This quota is calculated by taking the number of seats (3) and adding 1. The total number of votes is then divided by this number (4) and then adds one more vote.
The number of votes required in this example is 251.
The voting sees the red candidate elected with 380 votes, while the yellow candidate gets 200, blue candidate gets 160, the green candidate gets 160 and the purple candidate gets 100.
The red candidate has now been elected with 130 votes deemed surplus. Of their 380 next preferences, 160 are yellow, 100 are blue, 90 are green and 30 are purple.
Crucially, these are not simply treated as whole votes to then be divided amongst the remaining candidates. Instead, the surplus figure is used to determine the proportion of each vote that can be used.
The surplus for the red candidate (130) is divided by the total number of red first preference votes (380). This means that each of the red candidate’s next preference votes are valued at 0.342 each.
This means that the 160 next preference votes for yellow are transferred for 54.72 votes. Blue’s 100 next preference votes are worth 34.2 votes, green’s 30.78 and Purple’s is 10.26.
These are then added to the others’existing first preference votes, withYellow elected with 254.72 votes. Blue (194.2),Green (190.78) and Purple (40.26) each fail to attract enough votes at that stage.
The next stage continues with the same process, with surplus votes divided out among both the Blue, Green and Purple candidates.
If any of those candidates get enough of the surplus votes, they would be elected and the process would continue in the same manner. However, if none reach that quota, the lowest polling candidate is eliminated.
Eliminated candidates preferences are different from surplus, as all of the next preferences are counted as one vote, rather than a fraction of a vote.