Cash and vice.

The economy is turning over in the developed economies much more slowly than it did before the global crisis.

Historian Robert Murray writes in his new concise history of this country, The Making of Australia, that the half-million people who began to move towards self-governance in the middle of the 19th century were dealing with a host of controversies.

''Just a few: public versus church education; protection of industry versus free trade; the siting and funding of railway lines (and buildings, roads, hospitals and waterworks); payment of members of Parliament; protection of factory and mine workers; hours of work; jobs on the public payroll; and alleged 'obstruction' by Legislative Councils,'' Murray writes.

A very similar list exists today as the Abbott government prepares for a budget that, on the basis of its own pre-publicity, will be one of the most important in decades.

Budgets are always dealing with competing demands, and there are elements of pre-sale hyperbole in the picture Treasurer Joe Hockey is painting of the funding gap in the government's accounts, and the steps that he says need to be taken as soon as possible to close it.

Last Wednesday when he provided a glimpse of the budget-shaping report by the government's Commission of Audit that will be revealed in full next Thursday, he said for example that adjusted for inflation, government spending had almost tripled over the past 40 years, from about $6000 a head in 1973-74 to $15,000 a person today.

Australia's gross domestic product (GDP) has also risen, though. Adjusted for inflation, GDP per person has doubled in the past 40 years. Commonwealth government spending was 19.5 per cent of GDP in 1972-73, and peaked at 27.6 per cent of GDP in 1984-85, under the Hawke government. It was down to 23.1 per cent of GDP in 2007-08 as the global crisis emerged, hit 26 per cent in 2009-10 as crisis spending fed in, was down to 24.1 per cent in 2012-13, and is predicted by Hockey's midyear economic and fiscal outlook to be 25.9 per cent in the current year to June.

Hockey said this week that if spending was not reined in it would be 26.5 per cent of GDP in 2024, and that forecast highlights the fact that the short to medium-term problem the government faces is not a blowout in spending, but a squeeze on revenue.

Lower resources sector profits and tax payments are one reason. The economy is also turning over in the developed economies much more slowly than it did before the global crisis. Households are saving more, and spending more carefully.

Hockey is right that there is a longer-term structural problem, however. It's the one put in the spotlight by Peter Costello's first Intergenerational Report in 2003, and it is driven by two-sided demographics mainly: a shift by the baby boomers from earning income and paying tax to retirement, greater demand for healthcare and a reliance on retirement savings that more often than not are being supplemented by the government on one side; and a tightening of the government's revenue catchment on the other, as the ratio of workers and retirees changes.

Reserve Bank governor Glenn Stevens remarked at the beginning of this month that at the moment the number of people entering the labour force after finishing their education exceeded the number of people retiring. In about 10 years, however, the numbers would be roughly equal if labour participation rates stayed the same. The question then would be less '''Where will the jobs come from?' and more 'Where will the workers come from?''' Stevens said.

Hockey's heavy hints that the pension qualifying age must rise beyond the target of 67 years by 2023 that the previous Labor government set to 70 years is a response to the squeeze that Stevens refers to. It potentially strengthens the tax base and cuts the government spending base. Means testing for pharmaceutical benefits and other savings are also expected - but as Reserve Bank board member and economist John Edwards warned in an interview with The Wall Street Journal this week, the government has to be careful.

The economy is still making a precarious journey from reliance on the resources investment boom to more balanced and more traditional growth, aided by low interest rates. Hockey would like to see rates go even lower to give him more room to cut, but it's unlikely to happen.

Politics and economics are therefore both pushing the May 13 budget's heaviest hits into the years beyond 2014-15.

Labor is on the sidelines, arguing that the government is preparing to break its pre-election promise that the pension age would not be raised. Further increases in the pension age would be voted on before they occurred, however. So would be a mild increase in the GST, a yet to be announced piece of the jigsaw.

To argue that the government is breaking promises is in any event to ignore the big picture.

What is happening here is happening around the developed world, in countries including the US, Germany and Britain.

Governments are recasting and downsizing their pension, healthcare and social security commitments. It amounts not so much to broken promises or a breach of contract as a declaration of force majeure: an admission that commitments made in the past failed to understand what the transition of the baby boomers to retirement would do to government balance sheets that have now also been weakened by the global crisis.

The old commitments cannot be delivered - or at least cannot be delivered without poisonously large tax increases. It is what is, and Labor and the Liberals both see it.

mmaiden@fairfaxmedia.com.au