Cross-posted from Mark the Ballot.
There have been three national polls in the past two days:
- A Morgan poll at 47.5-52.5 in the Coalition’s favour (on the basis of 2010 preference flows) – a 1.5 percentage point movement to Labor on Morgan’s mid-week poll, but unchanged on last weekend’s poll.
- A Newspoll at 46-54 in the Coalition’s favour – a one point movement to the Coalition on the previous Newspoll.
- Essential has released its latest poll data (recasting the four previous rolling fortnights as weekly data). While the pathway differs a little, the endpoint is in the middle of the pack.
Turning to the Bayesian aggregation …
At this point in the blog, it is my normal practice to remind people that I anchor the above Bayesian aggregation with the assumption that the net bias across all of the polling houses sums to zero. You will need to come to your own view about where the actual level of collective systemic bias lies for all the pollsters. At the 2010 Election (with a different set of pollsters), the population voting intention was about one percentage point more in the Coalition’s favour compared with the pollster average (see here). In light of the 2010 experience, it is arguably plausible to subtract (say) half a percentage point or more from the above aggregation to adjust for the collective systemic bias across all of the polling houses. [As an aside, you will note that Simon Jackman, who seeks to anchor his Bayesian models with respect to the outcome of past elections regularly produces an aggregated poll that tracks well below the vast majority of individual poll results].
If we take a look at the longer-run series, at 46.9 per cent, Kevin Rudd as prime minister is polling around three percentage points better than the final months of Julia Gillard’s prime ministership.
And finally, focusing in on this latest Newspoll:
