When Treasury fingers superannuation as being the nation’s biggest tax concession, surpassing even owner-occupied housing’s privileges, you know super’s lurks are in the firing line.

When Tony Abbott rules out changes to super only in his first year as PM, you know both parties are taking aim – and that the opposition is hoping like crazy that Wayne Swan shoots first in May.

Today’s Treasury Tax Expenditure Statement reckons individuals’ superannuation concessions of one sort or another will cost the tax man $31.8 billion this financial year, overtaking housing’s $30 billion.

More impressive is that, on current policies with an aging workforce making the most of the opportunity, Treasury estimates super concessions will cost $34.6 billion next financial year, $39.6 in 2014-16 and $44.8 billion in 2015-16.

On top of individuals’ super tax breaks, the concessional taxation of employer contributions will cost another $13.2 billion this year – so $45 billion all up in super concessions.

Housing remains relatively stable, reflecting that with not much in the way of capital gains, owner-occupied housing being exempt from CGT isn’t costing much more.

Treasury reckons the “tax expenditure” for housing to dip from $30 billion this financial year to $29.5 in the next, recovering to $30 billion in 2014-15 and rising to $30.5 billion in 2015-16.

Together, superannuation and owner-occupied housing make up nearly two-thirds of all tax expenditures which, at $115 billion, represent 7.5 per cent of GDP this year.

It used to be worse. In Peter Costello’s last budget year, tax expenditures reached $126.5 billion – 10.7 per cent of GDP. As a percentage of GDP, Treasury forecasts tax concessions will dip another notch to 7.4 per cent next financial year before starting to rise again.

That’s not necessarily a reflection of the Labor government tightening up on tax perks and the coalition handing more out – there were more capital gains about in 2007-08.

There are other “interesting” tax expenditures for fiscally constrained governments to consider – the $4.2 billion in capital gains tax discounts for individuals and trusts, for example – but for treasurers of either party facing our demographic inevitabilities and education, welfare and infrastructure ambitions, it’s the big bags of money that will attract attention.

There are tax sweeteners for superannuation on the way in, while it’s accumulating and, most of all, on the way out again. Concessional rates of tax apply to a super fund’s earnings and payments are tax free no matter how wealthy an individual might be – and that’s without getting into some of the exotic engineering involving part-pensions and such.

The extent of the Howard/Costello super concessions overwhelmingly benefited those on the highest tax brackets and having been pegged back a little by Swan.

Many in the industry expected super’s massive tax advantages to be hit harder than they were in the last budget – but there’s another one every May.

Michael Pascoe is a BusinessDay contributing editor