Another 2.7% is the cyclical deficit, which should disappear of its own accord as the economy recovers boosting tax revenues and reducing unemployment benefit payments.

BBC: The Budget in numbers

One assumes that at some point things get back to normal and revenues begin to rise and the cyclical part of the deficit goes away.

FORBES: The Path To Profligacy

"We're in a much worse situation than in 1992 because more of this deficit is structural rather than cyclical and the entitlement explosion is closer at hand, " says Goldman Sachs chief economist William Dudley.

FORBES: Your Next Tax Hike

"The deficit will be reduced by the cyclical expansion that is now under way, which will absorb spare capacity in the economy, " Charles Collyns, deputy director of the IMF's Western Hemisphere Department, told reporters.

CNN: IMF: U.S. needs to balance budget

And if a bigger deficit than expected does open up for cyclical reasons, Mr Brown would be unlikely to need to try and close it.

ECONOMIST: Gordon Brown and the Bank