"My finance minister colleagues and I are resolute in our determination to use all policy levers to generate growth and jobs," he said. He had just made "Go for Growth" the unofficial slogan of the Brisbane G20 leaders meeting.

The Australian economy was growing faster than Britain's, faster than the United States', faster than Europe's, and faster than every other significant developed economy.

He exhorted his colleagues to try harder, to do "whatever it takes to boost growth and create new jobs". And he got them to commit to measures that would boost the size of their combined economies by more than 2 per cent over the next three years, "an unprecedented break from business as usual".

He is back at the G20 this weekend, in Ankara in Turkey. He is no longer the host and he is no longer riding high.

Australia's economy is growing more slowly than Britain's, more slowly than the United States', more slowly than Europe's, and more slowly than just about every other developed economy.

It could be worse, he told a Sydney press conference before he left on Wednesday. Australia could be in recession, like Canada. The figures he presented had Australia just whiskers away from recession. It's economy grew by just 0.2 per cent in the June quarter, mere notches above zero.

How did we get from there to here? If you want just one graph to tell the story, you can't go past the Reserve Bank's monthly update of commodity prices.

It's a picture of twin peaks. The price of the things Australia sells stayed low right up until the mid-2000s, then suddenly doubled, soaring to undreamt of heights in 2008 before collapsing in the financial crisis, then soaring back to an even greater height before collapsing from mid-2011. It's been plummeting nearly every month since, falling a few percentage points each time. Last month it fell 3 per cent.

The more commodity prices plunge, the more our national income slides unless it is counterbalanced by rising volumes of the things we are selling.

That's exactly what's been happening for the past two years. Rising volumes of exports have been offsetting the lower prices we get for them, until the June quarter when an unusually low volume of exports revealed there wasn't much else driving the economy.

As economist Andrew Charlton puts it: "The underlying data has been weak for at least two years."

Mining firms are slashing their investment and non-mining firms aren't lifting theirs fast enough to take up the slack. Low interest rates have been stoking a housing boom but not an investment or spending one. Consumers are shopping at a restrained pace and putting away money just in case. Household saving is at heights not seen in a generation.

The Reserve Bank governor Glenn Stevens believes there may be little point in cutting interest rates.

"It is not that monetary policy is entirely powerless, but its marginal effect may be smaller, and the associated risks greater, the lower interest rates go from already very low levels," he told a recent gathering.

He would like the government to spend big on infrastructure, but it's not keen to do that for financial reasons, announcing next to nothing new in the May budget. Fortuitously, it did spend big in the June quarter as it took possession of some really big pieces of military equipment. The big whack of cash was probably enough by itself to keep economic growth positive.

The dollar is sliding in line with sliding commodity prices, falling below 70 US cents after peaking at 105. It will help. Our businesses will find it easier to sell goods overseas, but we'll have to pay more for the things we import.

So far employment is holding up. One of the reasons is that we've been making ourselves cheap by accepting extraordinarily low wage rises. Echoing the Treasurer, one of the government departments sent a memo to its staff this week extolling the virtues of a 1.5 per cent pay offer. Its exact words: "It's better than 0.0 per cent."

Peter Martin is economics editor of The Age.

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