Yesterday, one reader commented on my simulation of the forthcoming South Australian state election that it was a "big assumption" to assume minor-party/independent (MPI) preferences could flow equally to the Greens as well as each other. The implication being that a candidate like David Winderlich would harvest more MPI preferences than the Greens and is therefore a higher chance of winning than the 20-30% I gave the micro-parties/independents.
Let's see, shall we? (Yes, I do requests!)
Since I had already set up the scenario for SA 2010 for the previous run, it was simple enough to make adjustments and run two new scenarios. The first new scenario is a set of simulations where Winderlich's vote climbs from 0% to 6% and everyone's preferences are distributed randomly. The second new simulation is similar. Winderlich's vote climbs from 0% to 6% but the random preference distribution is filtered so that minor party/independent candidates always preference him above the Greens.
The results are quite dramatic. If we consider winning 50%+ of scenarios to be a magic threshold for one seat, then in scenario one, with random preferences, Winderlich needs a vote of over 3.8% to get into that zone. In scenario two, with the micros preferencing Winderlich over the Greens, he only needs 2% of the vote. If a micro-party/independent candidate is preferenced by all other micro-party/independents above the Greens then the vote required to win a seat is cut in half.
From the curve of the graph, the highest rate of change in scenario two occurs when Winderlich's vote goes from about 0.5% to about 2%. What we can say from that is that in March 2010 there is a big difference in results between 0.5% of the vote and 2%, a much bigger change than going from, for example, 3.5% and 5%.
If we look at yesterday's scenario, the tight contest for the last seat means that the Greens are serious challengers while only winning in 26% of the simulations. Winderlich starts winning a seat in 25% of simulations on only 1.5% of the vote if he is preferenced above the Greens. However, his improved standing is achieved by freezing out the Greens, which also opens the door for the Liberal's fifth candidate, Rita Bouras, who starts winning the final seat in 23% of scenarios (up from 10% yesterday).
My gut instincts is that MPI candidates are more likely to preference other MPI candidates already, so I think we can say that 4% of the vote would guarantee an MPI candidate the seat. Futhermore, if this election there is some "small fish" candidate hostility to the "biggest small fish" (the Greens), and the Greens correspondingly get poor preferences, then we would have to rate much higher than I said yesterday the chances of a seat going to either the Liberals or the large field of micro-party/independent candidates.
The lesson from this is that if the micro-parties and independents preference each other exclusively ahead of the Liberals, Labor and Greens, they can definitely win one seat. I don't need to run a simulation to say that they would also put themselves in the running for a second seat too.
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