<p>The level of public borrowing plays a central role in UK government policymaking, especially in the run-up to each Budget. Accurate forecasts of the overall fiscal stance are crucial in assessing the general health of the economy, the direction of tax policy and the volume of public services that can be supplied. But these forecasts have a relatively poor record in the UK in recent years. The government's last Financial Statement and Budget Report noted that the budget deficit is the difference between two large aggregates of spending and receipts and forecasts of it are inevitably subject to a wide margin of error. Over the past five years the average absolute errors have been around 1 per cent of GDP, or plus or minus £8 billion in today's prices.</p>