Listening to the Treasurer and others, you may get the impression that a blowout in spending has caused a structural deficit. This does not accord with the analysis of the independent Parliamentary Budget Office. I alluded to this in my piece in the Guardian the other day, but I think it’s worth quoting the PBO at length:

…trends in the SBB estimates can be explained by changes in the structural levels of government receipts and payments. From the SBB peak in 2002-03 to its trough in 2011-12, the structural level of receipts excluding GST fell by around 5 percentage points of GDP. The structural level of government payments excluding GST over this period rose by around 1 percentage point of GDP and hence the SBB fell into deficit. Over the period 2011-12 to 2016-17 the structural level of receipts is expected to increase by approximately 1¾ percentage points of GDP while the structural level of payments is expected to decline by around 1 percentage point of GDP leading to the expected reduction in the structural deficit over the period of the 2013-14 budget and forward estimates years. 

Over two thirds of the 5 percentage points of GDP decline in structural receipts over the period 2002-03 to 2011-12 was due to the cumulative effect of the successive personal income tax cuts granted between 2003-04 and 2008-09. A further quarter was the result of a decline in excise and customs duties as a proportion of GDP. Significant factors driving this trend included the abolition of petroleum fuels excise indexation in the 2001-02 Budget and the decline in the consumption of cigarettes and tobacco over the period.

Structural payments (ie. spending) rose about 1 percentage point of GDP over the past decade, and they’re expected to fall by the same amount over the coming few years. Meanwhile structural receipts (ie. revenue, mostly from taxes) fell by about 5 points, and is only expected to rise by about 1.75 percentage points of GDP in the years to come. The problem is a revenue problem, not a spending problem.