Sunday, October 23, 2016

Early voters favour the Coalition

The Australian Electoral Commission publishes Two Candidate Preferred (TCP) results for each seat by vote type. From this data it would appear at all elections since 2004, early voters (ie. pre-poll and postal voters) typically favour the Coalition in comparison with ordinary voters in their home seat.

Provisional voters appear to favour the Coalition's opponent (which was Labor in the vast majority of these TCP cases). Absent voters are also more likely to vote against the Coalition when compared with ordinary voters in their home electorate (this trend appears to have intensified over time).

As a result, the final vote count (some two weeks after the election) has been more favourable to the Coalition than the ordinary vote count on election night might suggest. This is because the early voters outweigh (in both the extent of bias and the number of voters) the tendency of absent and provisional voters. (See yesterday's post for the proportion of votes by vote type for each election since 2004).

Sorry, but there are a lot of charts, which I will group by election year.

In looking at the histograms, look to where the 0 (zero) bias point lies in comparison with the peak or central tendency of the distribution. In the line charts, each line is a seat; look to whether they typically dip up or down compared with the ordinary votes.

Note: These charts do not include Labor v Other nor Other v Other TCP outcomes where they have occurred.






Saturday, October 22, 2016

Australian Federal Voting Practice

Today's charts take a quick look at the number and proportion of formal votes cast at recent Federal elections by vote type in the House of Representatives. Before each chart is a quick definition of the vote type.

An Absent Vote is cast on election day, but at a polling place outside of the voter's electorate, but still within the state or territory.

An Ordinary Vote is cast on election day at a polling place within the electoral division for which a voter is enrolled.

A Postal Vote is cast by post because the voter cannot attend a polling place in their state or territory on election day.

A Pre-poll Vote is cast at an early voting centre or an AEC divisional office before election day.

A Provisional Vote is one cast when a voter's name cannot be found on the certified list, the voter's name is already marked off the certified list as having voted, or the voter is registered as a silent elector.

Yielding a total formal vote count as follows.

A Formal Vote is cast when the ballot paper has been marked according to the rules for that election and can be counted towards the result. A ballot paper that does not meet the rules for formality is called informal and cannot be counted towards the result.

Sunday, October 16, 2016

Australian Election History

Note: the September 1940 election outcome is difficult to classify in this format. In a House of Representatives of 74 seats, it saw a hung Parliament. The Coalition and Labor each had 36 seats and independents had two seats. Following the election, the Coalition formed government with the support of the two independents (initially under Robert Menzies and then Arthur Fadden as Prime Minister). A year later, in October 1941, the independents switched their allegiance to Labor with John Curitn as Prime Minister. Curtin went on to win the 1943 election with a sizable majority.

The data for these charts came from Wikipedia.

Sunday, October 2, 2016

Confessions of a failed forecaster

Let's be frank: I had a shocking election. My aggregated forecast of 51.4 per cent for the Coalition in two-party preferred (TPP) terms was off, way off. The final outcome was a good percentage point lower at 50.35 per cent. 

My error was simple. I had assumed that the pollster biases from the 2013 election would be much the same in 2016. Ironically, I was alerted to the error of my ways shortly before the election when Nate Silver blogged in early June 2016
The good news is that, over the long run, the polls haven’t had much of an overall bias, having underrated Republicans in some elections and Democrats in others. But the bias has shifted around somewhat unpredictably from election to election. You should be wary of claims that the polls are bound to be biased in the same direction that they were two years ago or four years ago.
Although I run both 2013-biased and unbiased models, I doubled down on the middle ranked biased model without testing the robustness of my assumptions. To add insult to injury, my unbiased models came in much closer to the final result. The unbiased TPP model projected the Coalition would get 50.6 per cent of the TPP vote share. The unbiased primary vote model projected 50.5 per cent.

Now that I have got that off my chest, let's have a closer look at the path of the polls over the election period and evaluate the performance of the pollsters. If we anchor a daily walk of the TPP estimate from aggregating the polls to the election outcome, we get the following.

My results suggest that Ipsos was the most accurate pollster over the election period. But to be fair, There was only a whisker in it between Ipsos, Galaxy, ReachTEL and Newspoll.

These results also suggest that Turnbull snatched outright victory (albeit a slim one) from what looked like a hung parliament early in the longer-than-usual election period. The cloud of poll results in the last quarter of this period were the most favourable to Turnbull.

If we focus on the primary votes, the story becomes a little more nuanced. Over the course of the election period the majors - but particularly Labor - lost primary vote share to the Others. This movement from Labor to Others may have been behind the Coalition's whisper thin win in the end.

While the Greens improved on their 2013 result (from 8.65 to 10.23 per cent of the primary vote share), they under-performed against their pre-election polling. The Green's primary vote trajectory was downwards for most of the period

The Coalition did worse than 2013 with preference flows. If they had achieved the same preference flows in 2016 as 2013, they would have achieved a TPP vote share of 50.6 per cent. This is significant: Up until the 2016 election, it was possible that the historically low preference flows in 2013 where anomalous.

My suspicion is that we are seeing fracturing of he left in Australian politics, where more and more people who do not want to vote Coalition, also feel uncomfortable with Labor in the first instance (even though in most cases the preference from those voters ultimately flows to Labor).

Well that is enough confession for this Sunday. Over the coming months I will look at other aspects of the 2016 election in more detail. As polls this far out from an election are of little predictive value, I will take a holiday from poll aggregation for the next 12 to 18 months or so.