NSW State Election Contests: The Swing

This is the final in my series of NSW State Election Contests posts, previewing the interesting contests for election watchers beyond the obvious conclusion of the poll. I'll be back after March 26 to make more commentary. In this post I'll examine the swing.

What is the swing?
For those Lindy Hoppers out there I'm not talking about this, I'm talking about what is mooted to be one of the largest swings in Australian electoral history. The swing is a crude measure of the change in the two-party preferred vote since the last election. It is supposed to measure the change in preference of the electorate for one side of politics over the other. However it does have a number of flaws. It's not an entirely useful concept as in a multiseat parliament where each seat elects one candidate, the swing may not necessarily predict the outcome of the election particularly for close elections. It also doesn't reveal complexities in voter trends, such as the recent rise of the Greens, or shed much light on local contests with independents.

However as a single number to tell you how the election fares up for the major parties it's the best figure out there.

A brief comparison of past swings
Antony Green has an excellent post on his blog about past swings in Australian electoral history. Here's a few records since 1950 (prior to 1950 it is difficult to determine a 2 party preferred vote):

• Last NSW Election - 3.7% against Labor
• Record at a State Election - 14.6% against Labor in Victoria in 1955
• Record at NSW Election - 9.1% to Labor in the 1978 Wranslide
• Record at NSW Election for change of Government - 8.3% against Labor in 1988
• Record at Federal Election - 7.4% against the (dismissed) Labor Government in 1975

Polling 

There are four main polling companies that gather data for the NSW Election (although there are others). Two of these are commissioned by the two major newspaper organisations in Australia (Nielsen by Fairfax,  published in the Sydney Morning Herald and The Age, and Newspoll by Newscorp published in The Australian), another poll is done by Essential Media a social marketing and communications firm and the fourth by Galaxy Research another PR and communications research firm.

Here are the last four polls done by each firm. They all differ in their timing and methodology and the additional questions asked. I've listed the primary votes of Labor, the Coalition and the Greens and then the two-party preferred vote (2PP) as well as the swing.

Nielsen - Published 16 February - Swing 18%

Labor 22%
LNP 53%
Green 13%

Labor 2PP 34%
LNP 2PP 66%

Galaxy Poll - Published March 4 - Swing - 16%

Labor 23%
LNP 50%
Green 14%

Labor 2PP 36%
LNP 2PP 64%

Newspoll - Published 14 March - Swing 15%

Labor 26%
LNP 50%
Green 11%

Labor 2PP 37%
LNP 2PP 63%

Essential Poll - Published 18 March - Swing 17%

Labor 24%
LNP 54%
Green 12%

Labor 2PP 35%
LNP 2PP 65%

This sort of polling generally has sampling errors of a few percent so there's no clear trend up or down in the data. What is clear is that even the lowest swing is pointing towards what will almost certain be a record in NSW and likely a record nationally too.

Applying these results broadly suggest a result along the lines of:
Coalition: 65-71 (including 16 Nationals)
Labor: 13-19
Greens: 2
Independents: 7
Though as I outlined in my previous post, some of the independents are in for a tough fight whilst some Labor seats could be had by independents. A statewide swing doesn't tell you much about these local contests.

Some might suggest that at least part of the swing is due to other factors. I'll talk about two that are sometimes discussed:

Incumbency
It is suggested that incumbent candidates receive an advantage in elections. It's difficult to determine what the average advantage is, but it's usually assumed to be between 1 and 2%. With so many Labor members retiring at this election (18 vs 7 Coalition MPs) you might assume that this could affect the magnitude of the swing. However in a 93 member house the effect would be less than a half of a percent and not influence the result. It could lead to the loss of a seat that Labor would otherwise be able to retain if the seat with a retiring member is held by a margin close to the predicted swing, though only Campbelltown would fit this description.


An increase in the Green vote
An increase in the Green vote (assuming it's coming from what would otherwise be Labor supporters) would reduce Labor's primary vote and potentially its two party preferred vote through exhaustion of preferences. However given that the Green vote appears to have collapsed almost back to it's 2007 figure of about 9% (possibly from left voters switching back to Labor in a futile attempt to boost its primary vote) it's unlikely that the small increase in the Green vote will increase the swing by much.

Conclusion
Aside from a record breaker, there's nothing terribly exciting about the swing in this election. The 'Bazslide' (you heard it here first) is going to go down in the history books. I'll know what I'll be watching on election night - the Legislative Council and the local side contests.