Analyse the electoral systems used in Australia and how they shape representation and the formation of government

What this dot point is asking

SCSA wants you to understand that the way votes are counted is not neutral: the choice of electoral system directly affects which candidates and parties win representation, and therefore who forms government and exercises political power. You need to be able to describe the systems, compare their effects, and evaluate how democratic they are against principles such as one vote, one value.

The House of Representatives: full preferential voting

The House of Representatives is elected from 151 single-member electorates (divisions), each returning one member. Australia uses full preferential voting, also called instant-runoff or the alternative vote. Voters must number every candidate in order of preference (1, 2, 3 and so on) for the ballot to be formal.

To win, a candidate needs an absolute majority, meaning more than 50 percent of the formal vote. If no candidate has a majority on first preferences, the candidate with the fewest votes is eliminated and their ballots are distributed to the next preference marked. This continues until one candidate passes 50 percent.

This system tends to produce stable single-party (or coalition) majority government, because it favours larger parties and rewards the broadly acceptable candidate. It also allows voters to support a minor party first without wasting their vote, since preferences flow on.

The Senate: proportional representation

The Senate uses a proportional system based on the single transferable vote (STV). Each state elects 12 senators and each territory elects 2. At a normal half-Senate election, 6 senators are elected per state.

Candidates must reach a quota to be elected. For a half-Senate election the quota is calculated by the formula: total formal votes divided by (number of vacancies plus one), then add one. Surplus votes above the quota are transferred at a reduced (fractional) transfer value, and candidates with the fewest votes are excluded and their preferences distributed, until all vacancies are filled.

Because seats are shared roughly in proportion to vote share, the Senate is far more likely to elect minor party and independent senators (the Greens, One Nation, and others). This frequently denies the governing party a Senate majority, so the Senate acts as a house of review and a check on the executive.

Since 2016, Senate voting allows voters to vote above the line (numbering at least six parties in order) or below the line (numbering at least twelve individual candidates), which ended the old group voting ticket system that produced "preference harvesting".

How votes become government

Government is not formed by winning the most votes nationally; it is formed by the party or coalition that commands a majority on the floor of the House of Representatives (at least 76 of 151 seats). The party leader who can command that confidence is commissioned as Prime Minister by the Governor-General.

This means a party can win government with less than half the national two-party-preferred vote if its support is efficiently distributed across seats, and a hung parliament results when no party reaches 76 seats, forcing negotiation with crossbenchers (as in 2010).

Representation and electoral fairness

Australia promotes equality of representation through several features: compulsory enrolment and compulsory voting (enforced by the Australian Electoral Commission), independent redistribution of electoral boundaries to keep enrolments roughly equal, and the principle of one vote, one value within the House. The Senate, by contrast, deliberately gives every state equal representation regardless of population, so a Tasmanian vote carries far more weight than a New South Wales vote. This tension between equal representation of people and equal representation of states is central to evaluating how representative the system is.