Today the Australian Electoral Commission (AEC) released information confirming South Australia will lose one electorate, and Victoria and the Australian Capital Territory (ACT) will each gain one.
One year and one day after a new parliament sits, the AEC calculates the number of seats each state is entitled to. It does this by summing state populations, dividing that number by the number of members for the states (as stated in s24 of the Constitution), and then dividing the population of each state and territory by that divisor. This ensures each state and territory has a fair number of members in the House of Representatives. Further information on this allocation process is available in a Parliamentary Library FlagPost on representational entitlements, which includes links to the AEC’s thorough descriptions of the calculations and a link to the Australian Bureau of Statistics (ABS) data used for calculations.
Although South Australia’s population has grown by 0.6% during 2016, this growth was not as strong as most other states and territories—Australia’s total population grew by 1.6% over the same period. Therefore, South Australia’s population is no longer large enough to be entitled to its current allocation of 11 seats in the House of Representatives, necessitating a reduction of one electorate at the next Federal election. South Australia has had 11 seats since 2004; the reduction will take that state back to the number of seats it last had at the 1954 election, although it has had as many as 13 seats between 1984 and 1990.
Victoria and the ACT had the strongest growth with 2.6% and 1.7% respectively in 2016, and their populations are now large enough for them to be allocated one extra member for the next Parliament. This is a net gain of one seat in the House of Representatives, and so the 46th Parliament will have 151 members. The Parliament has had 150 seats since 2001, and has never before had more than 150.
A change in the number of Federal electorates in a state is the first of three triggers that mean the AEC must commence a redistribution (redrawing of electoral boundaries). Other triggers include an uneven number of electors across electorates within a state, or seven years having passed since the last redistribution.
The AEC must now redraw boundaries in South Australia, Victoria, and the ACT before the next election. Also on its work schedule is to complete the redistributions of Tasmania and Queensland (both triggered by the seven year requirement). Redistributions can take some time to complete; if an election is called before all redistributions are finalised the AEC must undertake ‘mini-redistributions’ for those states where redistributions have not been finalised. This is when, for brevity’s sake, two divisions are joined to reduce the number of electorates in a state, or two are split into three to increase the number of electorates—although the mini-redistribution provisions have never been used. More detail on mini-redistributions is in this FlagPost.