High-quality forecasting is an essential part of achieving value for money for the taxpayer. Since 2010, more than 70 of the NAO's reports have identified forecasting weaknesses. For example, the Department for Education initially underestimated the scale of demand for its academies programme and did not develop robust cost estimates. To remain within spending limits without restricting the pace or scale of the expansion, it used additional contingency funding of £105m and reassigned £244m from other budgets. 'Optimism bias' and poor quality data are among the root causes of departments' poor production and use of forecasts. Analysts have expressed concern that they are under pressure to provide supportive rather than realistic forecasts; and over half the analysts surveyed by the NAO identified a lack of good-quality data as preventing good forecasting. While the Treasury has introduced incentives to improve forecasting, these are at risk of being overwhelmed by the need to meet Parliament's requirements not to breach end of year spending totals. Most Finance Directors responding to the NAO survey considered that the spending control framework incentivised them to over-budget and underspend. In 2012-13, underspending increased to £11.5 billion, nearly three times the recent average. The Treasury encouraged underspends for Budget 2013; however, the NAO is concerned that the Treasury's flexing of the budget exchange rules (allowing departments to carry forward a forecast underspend from one year to the next) was not clearly related to the quality of individual departments' financial management