Australian STV (Hare-Clark)

Under the Single Transferable Vote (STV) system, voters rank candidates on their ballot in order of preference. A "1" is placed next to their highest preference, a "2" next to their second choice, a "3" for their third, and so on.

A candidate must reach a specific calculated number of votes, known as a quota. Any candidate who achieves this quota is elected. If a candidate receives more votes than necessary to meet the quota, those surplus votes are transferred to remaining candidates based on the voters’ next indicated preferences. The primary advantages of STV include the ability to elect multiple representatives simultaneously taking into account all of the voters preferences.

The main distinction between standard preferential voting and STV is the number of available seats. A basic preferential vote is typically used when there is only one single vacancy to fill. STV is utilized when there are multiple vacancies within the same contest. In these multi-seat elections, the tallying process uses the voters' ranked preferences to transfer surplus votes to ensure all available positions are filled efficiently.

To determine winners in a Single Transferable Vote election, ballots are counted in rounds. Lowest-performing candidates are eliminated one by one, and their votes are transferred to subsequent preferences to push others past the required quota.

The quota is calculated by dividing the total number of valid votes cast by the number of available positions plus one. For example, in an election with 115 total votes cast to fill 3 vacancies, the total number of votes a candidate will need to be elected is 28.75 votes.

Candidates who meet or exceed this quota are declared elected. If vacancies still remain, any surplus votes from elected candidates are transferred to subsequent preferences using the Unweighted Inclusive Gregory method, bypassing any candidates who have already been elected or eliminated. If no remaining candidate reaches the quota after a round of transfers, the candidate with the fewest votes is removed, and their ballots are transferred to the next listed preferences.

The required quota threshold can change during the counting process if votes become "exhausted." A ballot becomes exhausted when it cannot be transferred further because the voter either did not indicate subsequent preferences, or all of their indicated preferences have already been eliminated from the contest. Whenever a ballot becomes exhausted, it is effectively removed from the total count of active votes.

ElectionBuddy uses the Unweighted Inclusive Gregory Surplus Transfer Method. Under these transfer rules, if a candidate receives more votes than the required quota, a fraction of every ballot in their possession is transferred to the next valid preference indicated on that ballot. The transfer value is determined by the formula: (Total Surplus Amount) / (Total Number of Ballots Held by Candidate).

To illustrate this mechanism using the previously established figures: assume a total of 115 votes cast results in a required quota of 28.75 to win a seat. If a candidate successfully secures 45 total votes, they have met the quota and hold a surplus of 16.25 votes (45 minus 28.75).

This 16.25 vote surplus must then be distributed to subsequent preferences that have not already been elected or defeated. Based on these figures, here is a sample calculation demonstrating how the transfer value to the next preferences is determined.

Under STV, each voter casts a single ballot, ranking the candidates in order of their preference. A defining characteristic of this system is that ballots are transferred based on these voter preferences rather than being wasted.

STV is primarily used to ensure proportionality in election results and to facilitate consensus-building around popular candidates. By enabling the transfer of votes, this system mitigates vote wastage, where voter preferences are minimized once a single candidate secures a majority.

For further details, please visit Hare-Clark electoral system on Wikipedia and Single Transferable Vote on Wikipedia