Anybody who looks carefully at the world economy will recognise that a degree of monetary and fiscal stimulus unprecedented in peacetime is all that is prodding it along, not only in high-income countries, but also in big emerging ones. The conventional wisdom is that it will also be possible to manage a smooth exit. Nothing seems less likely. So let us consider the endgame, instead.

We must start from the reverse side of the stimulus coin: the private sector is now spending far less than its aggregate income. Forecasts in the Organisation for Economic Co-operation and Development's latest Economic Outlook imply that in six of its members (the Netherlands, Switzerland, Sweden, Japan, the UK and Ireland) the private sector will run a surplus of income over spending greater than 10 per cent of gross domestic product this year. Another 13 will have private surpluses between 5 per cent and 10 per cent of GDP. The latter includes the US, with 7.3 per cent. The eurozone private surplus will be 6.7 per cent of GDP and that of the OECD as a whole 7.4 per cent.

Moreover, the shift in the private sector balance between 2007 and 2010 is forecast to exceed 10 per cent of GDP in no fewer than eight OECD member countries (see chart). It is also forecast to exceed 5 per cent of GDP in another eight. In the US, it is forecast to be 9.6 per cent of GDP. In the eurozone, it is forecast at 5.5 per cent of GDP and in the OECD