Single Transferable Vote
The Single transferable vote (STV) is a system of preferential voting designed to minimize "wasted" votes and provide proportional representation.
To give you a bit of an introduction to how it works let's imagine a friend is going to Costcutters to buy their lunch and they ask you if you'd like anything. You quite fancy some crisps so reply that you'd like a bag of Salt & Vinegar, but if they haven't got any you'll have Ready Salted and if they have neither flavour just to get whatever.
What you're saying is that Salt & Vinegar is your first preference, Ready Salted is your second preference and after that you don't really mind what you get  you have no further preferences. This is essentially how the STV system works, you select your first preference but should that option be eliminated your second preference will come into play and so on until you either don't mind what (No Further Preferences) or if you do not want any of the remaining candidates you can vote to ReOpen Nominations (RON)  in our example this would be represented by not wanting any other flavours than Salt & Vinegar or Ready Salted.
In our example your preferences are used to choose which of the available flavours you would like  in the elecions the preferences come into play during each round of vote calculation. All votes are counted and the candidate who has received the least votes is eliminated, anyone who had voted for this candidate as their first preference now has their second preference vote allocated to their second preference candidiate and the process then repeats until there is a winner.
So in a nutshell you allocate your preferences to candidates until you are either indifferent to the remaining candidates (No Further Preferences or NFP) or you do not believe any of the remaining candidates are suitable for the post (ReOpen Nominations or RON)
* Single transferable vote technically only applies when two or more seats are available for a post, so during the Officer Elections the votes are known as eliminating instant runoff elections.
Example 1: One seat available. President of the Students’ Union.
Under this simple example there are five candidates, namely A, B, C, D and E. The number of first preference votes each has received is as follows:
Candidate

No. of First Preference Votes

Total Valid Votes: 4000

A

200

Quota: 2001

B

1000


C

1500


D

500


E

700


R.O.N.

100


In order to be elected a candidate needs over half of the valid votes at any stage. In this example, no candidate has reached the required number of votes, so we eliminate the candidate with the least number of first preference votes, R.O.N. and reallocate those votes to the second preferences.
Candidate

R.O.N.’s Redistributed Vote

Total Vote so far

Total Valid Votes: 4000

A

0

200

Quota: 2001

B

50

1050


C

0

1500


D

50

550


E

0

700


R.O.N.

100



Once again, no candidate has reached the required number of votes. This time candidate A is eliminated. This procedure follows until one candidate has exceeded the required number of votes to be elected
Candidate

A’s Redistributed Vote

Total Vote so far

Total Valid Votes: 4000

A

200


Quota: 2001

B

150

1200


C

0

1500


D

25

575


E

25

725


Candidate

D’s Redistributed Vote

Total Vote so far

Total Valid Votes: 4000

B

400

1600

Quota: 2001

C

100

1600


D

575



E

75

800


Candidate

D’s Redistributed Vote

Total Vote so far

Total Valid Votes: 4000

B

500

2100

Quota: 2001

C

300

1900


E

800



Candidate B is declared the winner as he has reached the required number of votes to be elected, despite Candidate C having more first preference votes than any other candidate.
Example Two: Two seats available. NUS National Conference Delegates
Under this simple example there are five candidates, namely A, B, C, D and E. The number of first preference votes each has received is as follows:
Candidate

No. of First Preference Votes

Total Valid Votes: 4000

A

200

Quota: 1334

B

1000


C

1500


D

500


E

700


R.O.N.

100


The required number of votes is calculated by:
<Equation: Total Valid Votes divided by (Number of Seats + 1)>
In this situation candidate C has reached the required number of votes. The difference between the number of votes required and gained is then discounted and redistributed to candidate C’s second preferences. Example: (1500 – 1334)/1500 = 0.11066 multiplied by the number of votes.
Candidate

C’s Discounted Vote

Total Vote so far

Total Valid Votes: 2666

A

200*0.11066

222.133

Quota: 1334

B

400*0.11066

1044.264


C

166

1334


D

300*0.11066

533.198


E

500*0.11066

755.33


R.O.N.

100*0.11066

111.066


No other candidate has reached the quota yet so the candidate with the fewest votes so far is eliminated and the votes redistributed until another candidate has reached the required number of votes.
Candidate

R.O.N.’s Redistributed Vote

Total Vote so far

Total Valid Votes: 2666

A


222.133

Quota: 1334

B

100

1144.264


C


1334


D


533.198


E

11.066

766.396


R.O.N.

111.066

111.066


Candidate

A’s Redistributed Vote

Total Vote so far

Total Valid Votes: 2666

A


222.133

Quota: 1334

B

200

1344.264


C


1334


D

22.133

555.331


E


766.396


Candidate B has now reached the quota and is also elected.
These are very simplified versions of how STV works. In reality our Elections are far more complicated mathematically to calculate. Thankfully your online votes are transferred directly into a computer programme so we can have the results within seconds!