This forecasting error was at least understandable since the dotcom boom was an exceptional episode, but the chancellor then started to bank on this buoyancy continuing.

ECONOMIST: Britain's budget

Of course, the financial crisis explains this massive forecasting error, but the study finds that relatively little was due to fiscal stimulus programmes in response to the downturn.

BBC: Debt and the crisis: How did governments get it so wrong?

Many thanks to Mike Cowan (author of the Cowan LRA Forecasting Model) for pointing out an error in a prior version of this post, and for providing the numbers behind the chart.

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