Defence spending is currently at about 2% of gross domestic product (GDP), or around A$56 billion per year. The Coalition is reportedly eyeing an increase to 2.5% of GDP by 2029.

The Albanese government’s current spending plan is expected to reach 2.33% of GDP by 2034. And in this week’s budget, it is expected to bring forward some of its already announced $50 billion increase in defence spending.

Why do these percentages matter? US President Donald Trump has made it very clear he expects America’s allies to pay more on defence, at least 3% of GDP.

We asked five experts if defence spending should be increased, and if so, by how much. They agreed more money is needed, albeit with caveats.