FRM Part II · FRM Exam Part II · The Art of Term Structure Models: Volatility and Distribution
A risk analyst at a bank uses the Ho-Lee model, dr = λ(t)dt + σ dw, to price interest rate derivatives. Which statement best describes the role of the time-dependent drift λ(t) in this model?
The time-dependent drift λ(t) in the Ho-Lee model is calibrated so model bond prices match the observed initial term structure. It is not a mean-reversion speed, does not shape volatility, and does not prevent negative rates, since rates are normally distributed.
- AIt is calibrated so the model's theoretical prices match the observed initial term structure of bond pricesCorrect
- BIt controls the speed at which the short rate reverts to a long-run mean
- CIt makes the volatility of the short rate decline exponentially with maturity
- DIt ensures the short rate cannot become negative
Explanation
In Ho-Lee, λ(t) is chosen as a function of time so that the model reproduces the current market term structure (a no-arbitrage fit). There is no mean reversion in Ho-Lee, volatility is constant, and rates are normally distributed so they can be negative.
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