How wide is the hung parliament zone?

Primary votes for major parties have hit a record low, and they may break that record this weekend. There are also more crossbenchers in the House of Representatives than ever before, with numerous other credible candidates threatening to produce an even larger crossbench in the new parliament. Certainly there is a lot of talk about a hung parliament.

But it would be wrong to assume that we have seen the last majority government, or that multi-party majorities in the House will be our universal experience.

The electoral system still gives a substantial bonus to the bigger parties, and there remains a real chance of this election, and any election held in a similar dynamic, to produce a majority for either Labor or the Coalition.

For this post I am refreshing a chart I originally built the night before the last election. It attempts to quantify the chances of a hung parliament based on the results of a previous election, quantified in terms of the size of the swing away from the government or towards the opposition.

For each of these elections, the light blue dot indicates how much of a swing would cost the new government its majority, and how much of a swing would give the new opposition a majority. This is based on two-candidate-preferred swings – so if there is a swing to the Coalition, that could involve them gaining Labor seats, or gaining Independent vs Liberal seats to reach a majority. Of course we wouldn’t expect to see uniform 2PP swings, let alone assuming that Labor or Coalition would have the same swings when their opponent is an independent or the other major party. But it gives you a sense of how wide a swing range might produce a hung parliament.

The hung parliament range used to be tiny. There were no crossbenchers elected in 1984 and 1987, and just one in 1990 and 1998.

The range became a lot wider in 2010, when there was actually a hung parliament.

Interestingly the hung parliament range was wider on the 2019 results than on 2022 results, despite the crossbench being much larger in 2022. I think this is mostly because so many of the crossbenchers elected in 2022 are on slim margins, so would lose their seats if that swing was on that scale and uniform.

This chart shows how the average margin of victory for crossbench MPs was one of the lowest in recent decades in 2022 – only 2013 was narrower, when Bob Katter’s margin was cut down and Clive Palmer and Cathy McGowan won their seats narrowly. Adam Bandt’s margin that year was also cut by him not having Liberal preferences.

If you were to assume that the independent MPs elected in 2022 would withstand any swing and the Coalition would need to regain their majority solely at Labor’s expense, the hung parliament zone would widen from about 3% to about 5%.

When you look at this data, it is clear that it isn’t hard to imagine a continued Labor majority – they just need to hold their own.

It’s quite possible that this election could produce a similar result to last time, with Labor maintaining their majority, but the first-term independents elected in 2022 could increase their margins. If this happens, the hung parliament zone following this election could become even wider, and thus the speculation about a hung parliament may be even more intense in 2028.

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