South Australia undergoes an electoral redistribution every four years, before every state general election.
The latest redistribution was undertaken in 2012.
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South Australia is the only Australian state where the Electoral Districts Boundaries Commission (EDBC) must take into account the political consequences of those electoral boundaries. The commissioners are required to draw ‘fair’ boundaries – defined as “if candidates of a particular group attract more than 50 per cent of the popular vote…they will be elected in sufficient numbers to enable a government to be formed.”
South Australia had a long history of malapportionment from the 1930s until the 1960s under the ‘Playmander’. Following the Playmander’s abolition, two elections (in 1975 and 1989) saw the Labor government re-elected despite not winning a majority of the two-party-preferred vote. In both these occasions, a hung parliament was elected and the government relied on independents to form a majority.
This history saw the institution, prior to the 1993 election, of the current ‘fairness’ criteria. This has seen each redistribution commission draw boundaries that give either side a majority of the seats if they win a majority of the two-party-preferred vote. On occasion this has had the effect of punishing MPs who managed to achieve, either through factors within or outside of their control, to gain a larger positive swing, or a smaller negative swing, against the trend of fellow candidates in the same party. In order to restore ‘fairness’, these seats often suffer greater changes, with more friendly areas removed to reduce the margin.
Despite these attempts to ensure ‘fairness’, the 2010 election saw the ALP win a solid majority of seats, despite losing the two-party-preferred vote. This was due to swings being very small (and in some cases swinging towards the government) in marginal seats, while facing large swings in safer seats.
The result shows the absurdity of attempting to impose ‘fairness’ on a system which by its very nature is not proportional or fair. Single-member electorate systems tend to produce results where one party wins and where election results are decisive – even when boundaries are drawn fairly, they do not ensure any sort of fair result or proportionality.
The 2012 redistribution decided not to attempt to redraw the boundaries to give the Liberal Party a majority of seats to reflect the last election result, judging that the previous redistribution was fundamentally fair, and that the redistribution commission is not responsible for the campaign, candidates or issues that led to a differential swing.
Overall, the redistribution saw only one electorate (on the EDBC’s estimate) switch from Labor to Liberal – the seat of Bright. Other seats had their margins changed, but no significant shifts.
For the purpose of this election guide, I will be using Antony Green’s margins, rather than those calculated by the EDBC.
On Antony Green’s margins, Bright remains as a marginal Labor seat, and no seats changed from Labor to Liberal.
Four marginal seats underwent changes that shifted their margin significantly: