Voting systems can generally be divided into three major groups:
The candidate who polls the highest number of formal votes, – even if that number is not more than 50% plus one of the formal votes – is elected.
Under the majority system, a candidate must receive an absolute majority of votes to be elected. The Commonwealth House of Representatives uses a majoritarian electoral system.
In Australia majority systems are sometimes called preferential systems. However, the term "preferential" refers to a voter being able to indicate an order of preference for the candidates on the ballot paper.
Exhaustive preferential (sometimes called Block Majority) is a variation of a majority system that can be used in multi-member electorates. Under this system, once a candidate is elected, all ballot papers are returned to the count to elect the next member.
Proportional representation systems are used for elections in multi-member electorates to elect candidates who receive a set proportion of the vote. In Australia, these systems are classified into two categories – List Systems and Single Transferable Vote (STV).
List Systems are used in multi-member electorates where the elector indicates an order of preference for the parties which then choose candidates to be elected as members of the parliament. In Single Transferable Vote, the voter indicates an order of preference for individual candidates.
All Australian Proportional Representation systems are STV types, although the South Australian, Western Australian and NSW Upper Houses and the Senate may be thought of as Semi-list Systems as the ballot paper provides for above the line voting or left and right of the line in the case of Western Australia.
The term preferential refers to the voter being required to indicate an order of preference for candidates on the ballot paper. Different types of preferential voting include:
- Full preferential – the voter must show a preference for all candidates listed for the ballot paper to be formal.
- Partial preferential – the voter must show a minimum number of preferences for candidates – usually equal to the number to be elected.
- Optional preferential – the voter need only indicate a preference for the candidate of his/her first choice and the allocation of any further preference is optional.
More than 50% of the formal vote.
Voters decide the successful candidates/s through a process of discussion, rather than by a formal vote.
More than one member is elected to represent an electorate at a single election.
A process of rotating candidates' names within a column on the ballot paper, so favoured positions (i.e. top and bottom of the ballot paper) are shared equally between all candidates. Neil Robson MHA, introduced these rotations to the Tasmanian Parliament in 1977.
The ACT adopted Robson rotation for elections to the ACT Legislative Assembly in 1995.
One member is elected to represent an electorate.
A written statement, registered with the electoral authority by a candidate or group of candidates, which expresses the order in which preferences are to be further allocated for an elector marking a "1" in one of the boxes in an above-the-line (SA, the Senate and also used in SA lower house when incomplete preferences are given by a voter) or left and right of the line (WA upper house) vote.