Australian STV is a form of Preferential Voting that uses the Hare-Clark tally method for calculation, with the Inclusive Gregory method being used to calculate the surplus transfer.
- Voting Process
- How to Set Up
- How Hare-Clark Preferential Results Are Calculated
- Inclusive Gregory Surplus Transfer Method
- Using STV for Ranking
Voting Process
Voters rank the candidates in order of preference, with “1” being the highest (most preferred) ranking. For example, if there are three candidates, the voter places “1” beside their 1st choice, “2” beside their 2nd choice, and “3” beside their 3rd choice.
To be considered a valid ballot, the submitted ballot must satisfy the following conditions:
- At least 1 candidate must be ranked for each position. In case abstention is allowed and the voter has abstained from voting for a position, the ballot may still count as valid for any other positions in the vote.
- No 2 candidates can have the same ranking, or the ballot is invalid (for that particular position only).
- Any candidate can be given any ranking, as it is the relative ranking that is counted. For example, in a vote for a position with 5 candidates, a valid ballot may be ranked “no selection/no selection/4th/5th/3rd”. In this case, the last candidate will be the 1st choice for this voter (since “3rd” is the highest-ranking marked on the ballot), followed by the 3rd candidate, and then the 4th candidate.
How to Set Up
On the Ballot Page, select “Preferential” from the voting systems drop-down menu. Doing so will populate a new drop-down menu where you choose between the 2 methods of calculating Results. Select "IRV or STV Hare-Clark"
Complete the setup as normal, leading to a ballot looking similar to the one below.
How Hare-Clark Preferential Results Are Calculated
Results are calculated through the process of redistributing the votes and eliminating low-ranked candidates in rounds to try and get a candidate across the quota of votes required to win. To generate a quota, the total number of submitted votes in a vote is divided by the number of available vacancies for the position plus 1. For example, if we have 115 votes cast in a vote where the position up for voting has 3 vacancies:
Candidates who meet the quota are elected. If positions remain to be elected the surplus votes are transferred to the next preference via Inclusive Gregory (skipping elected and defeated options). If no candidate reachs a quota in subsequent rounds, then the lowest ranking candidate is removed and their votes are transferred.
Inclusive Gregory Surplus Transfer Method
For the transfer of the surplus votes for Hare-Clark ElectionBuddy uses the Unweighted Inclusive Gregory Surplus Transfer Method.
In this case, if a candidate has surplus votes, then (surplus)/(# ballots for that candidate) votes get transferred to all that candidate's next preferences.
So, using the above example where the quota to meet is 28.75, with 115 total votes cast let's say a candidate ends up with 45 votes. 45 votes meets the required 28.75 quota, and leaves a surplus of 16.25 votes to be distributed to the preferences that are not already elected or defeated. Using the above example, here is a sample calculation to determine the surplus to be transferred to the next preferences.
Using STV for Ranking
STV is a great voting method when it comes to filling multiple vacancies, but there are some limitations to it that may make other voting methods a better option.
STV sets a quota that needs to be hit during each round. What STV doesn't do is rank each option; it just specifies which option achieved the necessary quota and continues to calculate rounds of voting based on the ranked voting choices by the voters until the vacancies are filled. Single Transferrable Voting (STV) will help you understand why a ranking is not possible given the calculation.
If ranking the winning candidates is the goal, you can download the results and manually calculate a winner using a method such as the Borda Count. You can also use Plurality Voting (also known as 'First Past The Post') and run multiple rounds of votes as separate new votes, more commonly known as 'runoff votes' until you have determined the rank order. Or you can do Scored Voting, but voters can assign the same score to multiple choices.
For any questions, please send us a chat using our Buddy Messenger in the bottom right of the screen.