FRM Part I · FRM Exam Part I · Calculating and Applying VaR
A portfolio manager has 250 daily historical returns and applies the age-weighted (BRW) historical simulation with decay factor λ = 0.98. The most recent observation has weight w1 = (1−λ)/(1−λ^250). Compared with the ordinary equal-weighted approach, what is the weight on the observation that is 1 day older than the most recent one relative to the most recent one?
The weight is 0.98 times that of the most recent observation. In age-weighted historical simulation, weights decline geometrically by the decay factor λ for each additional day of age, and normalization only scales all weights so they sum to one.
- A0.98 times the weight of the most recent observationCorrect
- B0.02 times the weight of the most recent observation
- C1.02 times the weight of the most recent observation
- DThe same weight, since all observations are normalized to sum to one
Explanation
In BRW, the weight on the observation i days old is λ^(i−1) times the weight on the most recent. So the observation one day older has weight λ = 0.98 times the latest. Option 0.02 confuses λ with 1−λ. Normalization changes the level, not the ratio.
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