The core concept is that a proper VaR model, for risk management purposes, needs to reflect how changes in positions affect risk. Using a "pseudo history" accomplishes this by applying the current positions to all historical scenarios, thus showing the impact of the position change on VaR. This directly addresses the prompt's scenario where a position reduction should be reflected in a lower VaR.

A is incorrect. Using the historical P&L before the position reduction would show no change in VaR, as the historical data hasn't changed. This defeats the purpose of assessing the impact of the manager's actions.

B is incorrect. Using the historical P&L after the position reduction also won't show the impact of the change. The new VaR would simply reflect the new, lower risk level, but not demonstrate the reduction itself.

D is incorrect. Comparing to a previous average VaR doesn't isolate the impact of the specific position change. Other factors could have influenced the previous year's average VaR.

Things to Remember

• For risk management, a VaR model should demonstrate how risk changes with position changes.
• "Pseudo history" is a key concept in achieving this, by applying current positions to historical scenarios.