The current boundaries have been used for the last three elections (first used in 2002). In future redistributions will fall due after every second election, but the current process was pushed back four years due to electoral changes made before the 2006 election.
Due to the lengthy period since the last redistribution, there has been a substantial amount of change in Victoria's population distribution. It's likely to result in a number of seats being abolished or changed radically.
The redistribution will affect the 88 seats in the Legislative Assembly as well as the 40 seats in the Legislative Council. The Legislative Council consists of eight regions, each electing five members. Each region consists of 11 lower house seats, meaning that any change in lower house boundaries will flow on to the upper house.
Like with any electoral map, the process of redrawing Victoria's electorates is affected by the major geographical barriers that cross the state. Victoria's barriers are much simpler and less obtrusive than those in New South Wales.
There is a line that divides the state in half, running through Melbourne and regional Victoria. This divide consists of Port Phillip Bay, the Yarra River and the Great Dividing Range.
On the current electoral boundaries there are 45 seats to the north and west of this line, and 43 seats to the south and east. A majority (32/55) of seats in the Melbourne metropolitan region lie south of the river, while a majority of country seats (22/33) lie to the west of the Yarra River and the Dividing Range.
The eight upper house regions largely reflect this divide. The four regions of Western Metropolitan, Northern Metropolitan, Western Victoria and Northern Victoria lie on one side of the divide, while Eastern Metropolitan, Southern Metropolitan, South-Eastern Metropolitan and Eastern Victoria lie on the other side.
The seat of Eltham, on the north side of the Yarra River, is included in Eastern Metro along with ten south-side seats. Every other region sits entirely on one side of the divide.
The Yarra River stands out as a clear divide through Melbourne when you look at a map of the state's electorates. Labor holds every seat in Melbourne north of the river. While Labor also holds a block of seats in the south-eastern corner of Melbourne, they only hold one seat on the immediate south side of the river: Alfred Park. Once you reach Prahran, the Yarra River operates as the boundary between Labor seats and Liberal seats all the way to the edge of Melbourne.
These eight regions are also useful in analysing what is happening in each part of the state. While nearly every seat will be changed in some way, there are some areas where large population movement will result in major change, while in others there will only be some minor tinkering to balance out seat totals.
Antony Green has produced helpful tables showing the population for each upper house region.
The biggest variations are in Western Victoria and Western Metropolitan, which are collectively 1.45 over quota. The growth in Western Victoria can largely be handled by transferring about half of one seat to Northern Victoria, which is 0.48 under quota. Western Metropolitan, however, is almost big enough for twelve entire seats to be drawn in the space currently covered by eleven. Northern Metropolitan is slightly over, while Southern, Eastern and South Eastern metro regions are under 1.39 under quota.
If you just look at current population numbers, there is an immediate need to create a new seat in Western Metropolitan and abolish a seat in Eastern Metropolitan. Future population growth, however, suggests that more dramatic changes are needed.
While there is no specific quota that needs to be met, the commissioners are required to consider future population growth when drawing boundaries. Population projections over the period of this redistribution (up to 2018) suggest that there will be substantially more growth at the western and northern fringes of Melbourne.
If the commissioners are to take into account population growth, they may look to create a second new seat north of the divide and abolish another seat to the south. This would likely result in a new seat at the northern edge of the Northern Metropolitan the abolition of another seat in the south-east of Melbourne. It is also possible that a seat could be created that crossed the Yarra River, but this would go against long-standing precedent.
These changes will have knock-on effects on the upper house regions. Obviously these boundaries will change all over the state, but in areas where seats are abolished or created, seats may have to be moved between regions to account for the change. Western Metropolitan will almost certainly need to transfer one of its seats into Northern Metropolitan, which will then need to transfer 1-2 seats into Southern or Eastern Metropolitan. It is likely that Eastern Metro will become more of a trans-Yarra region, with 2-3 seats north of the river.
These changes are likely to benefit Labor in the lead-up to the 2014 election. The Coalition won a slim 45-43 majority in 2010. With most of the growth happening in solid Labor-dominated areas, it seems certain that Labor will gain at least one seat in the redistribution. Thus the parties will enter the race in 2014 effectively tied 44-all, before a single vote is cast. The Baillieu government will need to do more than hold their current seats if they are to win a second term.