Chapter 13: Valuation of investments (2) Flashcards
e. Introduction to fixed income option pricing
Give four reasons why interest rate derivatives are more difficult to value than equity derivatives.
- The behaviour of an individual interest rate is more complicated than that of a stock price, as interest rates vary by term.
- For many products, it is necessary to develop a model describing the behaviour entire yield curve, whereas Black-scholes model of share option prices is based on single share price only.
- Volatilities of different points on yield curve are different
- Interest rates are used for discounting as well as for determining payoffs from derivative.
e. Introduction to fixed income option pricing
State Black’s formula for the price of a call option, defining all notation used.
c = P(0, T)[ F_0*Q(d1) - XQ(d2))]
where:
- Q(x) is the cumulative standard normal distribution function
- d1 = (ln(F_0/X) +0.5VT)/squrt(VT) and d2 = d1 - squrt(VT)
- P(0, T) is discount factor from strike date T back to time 0
- F_0 is forward price of the underlying asset
- squrt (V) is the volatility of forward price
- X is option strike price
(When valuing the option, we assume that the distribution of the value of the underlying asset is normally distributed)
e. Introduction to fixed income option pricing
State Black’s formula for the price of a put option.
p = P(0 T)[XQ(-d2) - F_0Q(-d1)
e. Introduction to fixed income option pricing
State the two approximations involved when interest rates are stochastic.
Approximations
- The expected value of VT is assumed equal to its forward price F0.
- The stochastic behaviour of interest rates is not taken into account in the way the discounting is done.
These two assumptions have exactly offsetting effects, when the model is being used to value an option on a (bond or other derivatives consider in this chapter)
e. Introduction to fixed income option pricing
State Forward price of coupon-bearing bond.
F_0 = (B_0 - I)exp(rT) = (B_0 - I)/(P(0, T)
Where:
- B dirty price of
- I is the present value of the coupons paid by the bond for duration T
- r is the risk free rate of interest compounded continuously
- T time to maturity of option
(F_0 can then be used in Black’s formula to value bond options)
e. Introduction to fixed income option pricing
Explain what is meant by the following in relation to a coupon bearing bond.
1. the clean price
2. the dirty price
3. accrued interest
- Clean price
- quoted price of the bond which appears on the dealer’s screens and does not include accrued interest - Dirty price
-clean price plus accrued interest
- it is the price at which the bond is traded.
- represents discounted present value of future cashflows paid by bond - accrued interest
- proportion of the next coupon deemed to have accrued since the last coupon was paid
e. Introduction to fixed income option pricing
State a formula relating to price and yield volatilities of a bond.
s.d = Dy0s.d_y
- s.d is forward price volatility
- s.d_y is the corresponding forward yield volatility
- D is (modified) duration of forward bond underlying option
- y0 is initial (forward)yield on forward bond underlying option
(This is needed since yield volatilities are usually quoted, but price volatility is used in Black’s formula)
e. Introduction to fixed income option pricing
State a formula for the modified duration in terms of the duration for a fixed interest bond.
Modified D = D/(1 + y/m)
Where m is the frequency per annum with which y is compounded.
e. Introduction to fixed income (Interest rate caps and floors) option pricing
Describe how interest rate caps and floors work.
- OTC derivatives that can be purchased from investment banks.
Cap:
- in return for initial premium it provides a payment each time floating rate R_K rises above fixed cap rate R_X
- Can be used to cap interest rate paid, e.g., on a mortgage
- it can be viewed as a pf of put options on a zero-coupon bonds
Floor:
- buyer receives a payment each time floating interest rate falls below fixed floor rate
- Can be used to provide insurance against a fall in interest rates on a floating rate note.
Both can be used to hedge against movements in ST interest rates or to speculate on such movements.
e. Introduction to fixed income (Interest rate caps) option pricing
Explain how each payoff is determined for a caplet.
- In each subperiod of interest rate cap, interest payment is made under relevant caplet if the floating rate in that subperiod exceeds the cap rate. Otherwise no payment is made in that subperiod.
- Interest payment made at end of sub-period
- Interest payment based on interest rate that applies over subperiod at start of subperiod
- Actual monetary payment based on payment in interest rate terms, multiplied by both cap principal and length of sub-period (or tenor)
(Payments are likewise made under a floor if the floating rate is less than the floor interest rate)
e. Introduction to fixed income (Interest rate caps and floors) option pricing
State the formulae for the payoff from a caplet and a floorlet.
Caplet:
Ltenormax(R_X - R_K,0) –> each payment is like a call option on LIBOR
Floorlet:
Ltenormax(R_K - R_X, 0)) –> each payment is like a put option on LIBOR
where:
- L is the principal
- tenor = t_k+1 - t_k (time between resets)
- R_K is floating rate (compounding frequency = tenor)
- R_X is the cap rate (compounding frequency = tenor)
e. Introduction to fixed income (Interest rate caps and floors) option pricing
Outline in words how to value an interest rate cap and an interest rate floor.
- Each interest rate caplet valued using Black’s formula.
- This values cap as call option on floating interest rate, with strike price equal to cap interest rate
- Value of interest cap is then sum of values of constituent caplets.
- Likewise, floor valued as sum values of constituent floorlets, where each floorlet valued (Using Black’s formula) as put option on floating rate, with strike rate equal to floor interest rate.
e. Introduction to fixed income (Interest rate caps and floors) option pricing
State the formulae for valuing an interest rate caplet.
c = LtenorP(0, T_k+1)[F_K * Q(d1) - R_X * Q(d2)
Where:
- d1 = (ln(F_K/R_X) + 0.5v_K * t_k)/sqrt(v_kt_k) and d2 = d1 - sqrt(v_k*t_k)
- F_K is the forward rate between t_k and t_k + 1
- squrt (v_k) is volatility of forward rate
squrt(v_k) can be spot volatilities or flat volatilities. spot v curves are humped, flat also humped but less so. flat are cumulative averages of spot v.
e. Introduction to fixed income (Interest rate caps and floors) option pricing
State the formulae for valuing an interest rate floorlet.
c = LtenorP(0, t_k+1)[R_X * Q(-d2) - F_K * Q(d1)]
e. Introduction to fixed income (Interest rate caps and floors) option pricing
State the put-call parity relationship between swaps, caps, floors.
cap price = floor price + value of a swap
Where:
- cap interest rate and floor interest rate are same
- terms, principals, frequency of payments etc are same
- swap is the agreement to receive floating and pay fixed