With the new Newspoll quarterly aggregates out, we can combine these State based breakdowns with the breakdowns from the 2 Nieslen polls taken over the same period and run some election simulations to find out what would most likely have happened were an election held last quarter and had results the same as the polling.
You can the see the mechanics of how the monte carlo simulation works over here.
The only difference is that for this sim I used 20,000 iterations rather than 10,000 and have adjusted the simulation to take into account the uncertainty involved caused by the polling itself – via a widening of the standard errors attached to the swing in each state, based on the respective State sample sizes of the aggregated polling.
After running our 20K elections, the results come in like this:
That first chart shows the distribution of the simulation results in terms of the number of ALP seats gained, where the most frequent result was a 17 seat gain to the ALP.
You might also notice that the shape of that distribution is close but not quite perfectly normal (or isn’t perfectly like a bell curve) – that’s a consequence of where the seats sit on the pendulum in each State relative to the swing suggested by the polling in each State.
The last two charts are by far the most interesting – they give the implied probabilities of the number of seats gained, should an election have been held and the polling results replicated (where the sim takes account of the margin of error of the polling)
Those last two charts are basically identical, where only the bottom axis has been changed – where one chart represents the results of the simulation as the number of seats gained by the ALP, while the other represents the results as the number of ALP seats there would be in a new hypothetical Parliament.
To read the charts, simply choose a seat number on the bottom of those two charts, trace up until it intersects the red line, then trace across to the left to read the associated implied probability. This tells us the probability that the ALP would have gained *at least* that number of seats were an election held over the last 3 months where the results replicated the polling.
For instance, there is just over a 60% implied probability that were an election held and the results replicated the polling, the ALP would have gained at least 16 additional seats.
Similarly, using the other chart, if an election were held during the last 3 months etc , there was just over a 50% implied probability that the ALP would have 100 seats in the new Parliament.