Antony Green’s ABC 2007 Election Guide has hit the web, and as usual it contains most things you wanted to know but were afraid to ask – and more – including new bells and whistles.

The latter include a “calculator”, where you can push a swing-lever and watch not only the seat numbers change, but individual seat margins as well.

You can also enter values on the calculator, and then play with a “Link this to outcome” option. You make your settings, press the button and it generates a URL which can be posted on blogs and websites so people can share their predictions.

The calculator assumes uniform swing plus some extra Antony magic. For example, there is the option of factoring in an estimate of retiring candidates’ personal votes, which explains why the starting point of a zero swing gives two Labor seats (Isaacs and Cowan) to the Coalition and one Coalition one (Makin) to Labor.

The individual seat margins, while great fun to play with, are not terribly realistic, because swings are never remotely uniform. Instead, Mackerras “pendulum theory” assumes that the deviations cancel out.

We can illustrate this with the 2004 election. It saw a 1.8 percent national swing to the Coalition, but individual seats went all over the place, from 9.1 percent to the government to 4.5 percent to Labor. The pendulum “worked” because if you had plotted a 1.8 percent swing on the pre-election pendulum it would have added a net five seats to the Coalition’s tally – very close to the actual change of four.

But that four actually comprised eight seats going from Labor to the Coalition and four going the other way, and no-one on earth could have made a calculator that would have produced this precise result from a 1.8 percent swing.

That is not a criticism of the calculator but a product-warning not to take individual seat margins literally. It is a fun way to get a feel of the House of Representatives landscape, and the state components are particularly illuminating.

No-one knows more about Australian elections than the one man institution Antony Green, and among all the pretty pages are his usual wise words.

We commend this Election Guide to the House.