past patterns of price movement. The financial crisis has revealed, however, severe problems
with these techniques. They suggest at the very least the need for significant changes in the
way that VaR-based methodologies have been applied; some, however, pose more fundamental
questions about our ability in principle to infer future risk from patterns observed in the past.
Four categories of problem have been distinguished in The Turner Review (FSA 2009a), and
are described in Chapter 25.
A primary message of the financial crisis was that the very complexity of the statistical
methods used to measure and manage risk made it increasingly difficult for an analyst to
convey the approach adopted and the content of the analysis, and for top management and
boards to assess and exercise judgement over the risks being taken. Statistical and mathematical
sophistication ended up not containing risk, but providing false assurance that the emerging
risks could be safely ignored.