The Australian has given us all a Boxing Day surprise by releasing a South Australia state voting intention poll for the October-December period in today’s edition. The poll surveyed 885 South Australian voters and returned topline primary vote figures of Liberal 40%, Labor 37%, Nationals 1%, Greens 9% and Others 13%. Newspoll extrapolates a Liberal TPP of 51% from these primary vote figures. This is a 6% fall in the Liberal TPP since the last quarterly SA Newspoll for the July-September period. Full details for the poll and the accompanying story can be found at The Australian.
As has become habit on this site we will undertake a seat projection based on this poll. The methodology for South Australian state seat projections can be found in our previous SA state seat projection posts here.
As noted previously, the seat projection model uses 2012 redistribution figures and does not take any sophomore or retirement effects into account.
The seat projection is set out below.
The above seat projection is a net improvement of 7 seats for Labor from the previous SA seat projection for the July-September Newspoll which returned a Liberal majority of 9, (Lib 28, ALP 16, IND 3).
As noted previously the SA seat projection methodology does not apply a state-wide uniform swing in isolation. The uniform state-wide swing is adjusted by seat taking into account the combined deviation from the cumulative TPP swing for the 2006 & 2010 elections for each respective seat.
Using the Mackerras pendulum with the TPP swing of 0.6% to Labor implied by the Oct - Dec 2012 Newspoll one would find no change in seat composition (ALP 26, Lib 18, Ind 3) in the House of Assembly.
However, given the lopsided nature of the division of marginal seats (Labor holds 10 seats with a TPP of 55% or less, the Liberals hold only 4 such seats) and the relative swings to the Liberals the model assigns to seats which resisted the state-wide swing to the Liberals in 2010 such as Newland and Hartley, the seat projection shifts 3 seats to the Liberals, eliminating the Government’s majority.
A few new features
Today we have included a few new features in the seat projection to quantify the uncertainty in the seat projection. Frequent readers will know that the seat projection is at its heart a collection of probabilities. In this instance the SA seat projection is a collection of 44 binomial probabilities (all seats except those held by independents). The central forecast of the seat projection is computed by adding these probabilities together. However this only shows the most likely outcome and not the full range of outcomes.
To give a full range of likely outcomes we have put the 44 binomial probabilities through a 20,000 simulation Monte Carlo process. Included in the above seat projection are the range of seats here we expect the result to fall within given a 95% probability threshold. In other words there is only a 1 in 20 chance that an election based on current Newspoll figures would fall outside of the ranges identified.
In today’s projection the top of the Liberal seat range is 24 seats, therefore a majority Liberal government is not out of the question on these figures, although it is very unlikely. We can also calculate the probabilities of the likely outcome based on the current Newspoll figures. These probabilities are set out in the pie chart below.
While a hung parliament is the most likely outcome, a Labor majority government is a significant possibility. A Liberal majority government is the least likely option but not impossible.
One Last Note
The above seat projection is a good approximation of what would happen if an election was held today. However the next SA election is not until March 2014 and a lot can still change in 15 months.