Ways to vote · Single transferable vote
Ranked choice · one or several winners
The single transferable vote
Voters rank the options, and several winners are chosen so that each part of the group is represented in proportion to its size. If a voter's first choice is elected with votes to spare, or is eliminated, their vote passes to their next choice.
Video
This video by CGP Grey explains how the system works.
How it works
- Each voter ranks the options in order of preference.
- A quota is calculated. Any option with more votes than the quota is certain to win a seat. It is the number of ballots divided by one more than the number of seats, so with 30 ballots and 3 seats it is 7.5.
- An option with more votes than the quota is elected. The votes it does not need are passed on to each voter's next choice at a fraction of their value, so that no vote is counted twice.
- If no option has reached the quota, the option with the fewest votes is removed and its ballots are passed on at their full value.
- This repeats until every seat is filled.
An example count
Thirty residents are electing three people to a committee from six candidates. Press Play the count to go through it round by round, or use the arrows.
The 30 ballots
| Number of ballots | Ranking |
|---|---|
| 10 | Amara Okafor → Ben Hughes → Dev Patel |
| 3 | Ben Hughes → Amara Okafor |
| 5 | Carmen Ruiz → Eun-ji Kim → Felix Moreau |
| 3 | Eun-ji Kim → Carmen Ruiz |
| 3 | Dev Patel → Ben Hughes |
| 2 | Felix Moreau → Carmen Ruiz → Eun-ji Kim |
| 2 | Felix Moreau → Dev Patel |
| 2 | Eun-ji Kim → Felix Moreau |
Why votes are transferred as fractions
When a candidate has more votes than they need, the extra votes are passed on to the voters' next choices. Rather than choosing which ballots to move, every ballot for that candidate moves on at a fraction of its value. In the example, Amara needs 7.5 votes and has 10, so she has 2.5 to spare. Each of her ten ballots passes a quarter of a vote to its next choice, and the other three quarters stay with her. This way no vote is counted twice, and no vote is wasted while it could still help elect someone.
What the quota is
The quota is the number of votes a candidate needs to be certain of a seat. It is the number of ballots divided by one more than the number of seats. With 30 ballots and 3 seats it is 30 ÷ 4 = 7.5. Four candidates cannot all have more than 7.5 votes out of 30, so anyone above the quota is sure to be one of the three winners. With one seat, the quota is half the ballots, so the winner needs a majority.
Strengths
- Very few votes are wasted.
- A third of the voters can expect to elect about a third of the winners.
- Voters gain nothing by ranking dishonestly.
- With one seat, it works the same as instant runoff.
Weaknesses
- It is too slow to count by hand for a large group, so a computer does the count here.
- The result takes some explaining, which is why each round is shown.
- Ranking a long list takes time.
Suited to electing a committee or a board, picking a shortlist of three, choosing dishes for a shared meal, or deciding which five ideas to fund.
Read more
Votes on this site are counted using the OpenTally model rules for the weighted inclusive Gregory method, which Scottish council elections have used since 2007. All values are kept as exact fractions and are only rounded for display. A tie is broken using the candidates' totals in earlier rounds. If they were tied in every round, the tie is broken by a random draw based on the vote's ID, so everyone who views the results sees the same outcome. Options that received no votes are removed together.