Every three years, approximately one year after the federal election, Australia’s population is assessed, and each state and territory is given a set number of seats to be filled in the next Parliament, based on population. When the number of seats allocated to a state changes, a redistribution is immediately triggered to draw up new electoral boundaries.
This time around, population shifts have guaranteed that New South Wales will lose its 48th seat, and Western Australia will gain a 16th seat. It now appears that the ACT’s population will not be sufficient to give them a third seat, after it first appeared to be possible in late 2013.
These redistributions will by necessity cause significant changes to borders, in order to create a whole new seat in WA and squeeze NSW’s populations into 47 seats.
Electorates will need to be drawn to be within two quotas. A quota is drawn up as the average population per electorate as of the time of the redistribution, and another one which is the average projected population of each new electorate as of 3.5 years after the conclusion of the redistribution. These quotas will be 1/47th of the NSW population, and 1/16th of the WA population.
Below the fold, I’ve posted my analysis of the likely trends in the NSW redistribution, and have produced an interactive map showing the population quotas in each electorate.
In short, I think the seat most likely to be abolished is Hunter, which will have significant knock-on effects in the Hunter region and in western NSW. Seats in inner Sydney will shift east, while seats throughout Western Sydney will expand in size in southwestern direction, shifting Werriwa and Macarthur further into the fringe of Sydney.
I’ll be back tomorrow with a similar analysis of the prospects in Western Australia.
In New South Wales, you’d expect the average electorate to be under quota, as there will be less seats at the next election then there is now.
Yet despite this trend, eleven seats have such a large population that they will exceed the larger quota in the redistribution. Another 8 seats are less than 1% under quota.
The four most populous seats in the state follow a line along the southern shore of Sydney Harbour from Wentworth to Reid, through Sydney and Grayndler. Each seat is slightly less populous than the one before it, but collectively these four seats are 16.8% over quota. The only solution will involve shifting each seat slightly to the east, until Reid can distribute surplus population to neighbouring electorates.
On the north shore, the coastal seats of Warringah and Mackellar are just over quota, with North Sydney and Bennelong just under quota.
There is a large block of seats, including Bradfield, Berowra and all of Western Sydney, where all but one seat sits under quota. Berowra and Werriwa are at approximately 94% of a quota each, and Chifley is just over the quota.
Overall the effect in this area will be to expand the size of most seats and shift them in a south-westerly direction, forcing Werriwa further into Campbelltown and Macarthur out to Picton. It is unlikely that the numbers will require a seat in Western Sydney to be abolished.
The situation is slightly more dire in the north of the state. Adding together the four North Coast seats, the two Central Coast seats and the five seats in the Hunter, this area does not include a single seat that reaches the quota, and overall these eleven seats are 53.7% under quota.
Thus I think it is most likely that the seat to be abolished will be in the Hunter region, and I would nominate the large semi-rural seat of Hunter as the best pick to be abolished. The eastern half of the seat, including parts of Maitland and Cessnock, would be transferred into other Hunter seats to bring other seats up to quota, while the western half would shift to be part of a western NSW seat.
It is not clear to me how western NSW would be divided up, but the addition of half a seat’s population from the upper Hunter will likely require significant redrawing of western seats, which are themselves under quota, so that by the time you reach the south-east of NSW, these areas are only about 30% over quota. This 30% over quota will drag Hume south and west, and make Macarthur more of a semi-rural fringe seat.