1 Determination of Forward and Futures Prices Chapter 5

2 Consumption vs Investment Assets Investment assets are assets held by significant numbers of people purely for investment purposes (Examples: gold, silver) Consumption assets are assets held primarily for consumption (Examples: copper, oil)

3 Continuous Compounding In the limit as we compound more and more frequently we obtain continuously compounded interest rates $100 grows to $ 100e RT when invested at a continuously compounded rate R for time T $100 received at time T discounts to $ 100e -RT at time zero when the continuously compounded discount rate is R

4 Conversion Formulas Define r : continuously compounded rate R : same rate with compounding m times per year

5 Examples Bank account pays 4% compounded monthly What is the (annual) continuously compounded returns? r = 12ln(1+.04/12) = 3.993% What is the future value of $100 dollars in 15 months? FV = 100exp{.03993x15/12} = $ or FV = 100(1+.04/12) 15 = $

6 Notation S0:S0:Spot price today F0:F0:Futures or forward price today T:T:Time until delivery date r:r:Risk-free interest rate for maturity T

7 Gold Example For gold F 0 = S 0 (1 + r ) T (assuming no storage costs) If r is compounded continuously instead of annually F 0 = S 0 e rT

8 Extension of the Gold Example For any investment asset that provides no income and has no storage costs F 0 = S 0 e rT

9 Suppose F > Se rT T = 0 CF0 sell forward: 0 buy spot: -S borrow r: +S Net cash flow: 0 Arbitrage portfolio T=1 CF1 Deliver: +F Payoff debt: -Se rT Profit = F - Se rT

10 When an Investment Asset Provides a Known Dollar Income F 0 = (S 0 – I )e rT where I is the present value of the income

11 Suppose F > (S – I)e rT T = 0 CF0 sell forward: 0 buy spot: -S Sell Income +I borrow r: (S-I) Net cash flow: 0 Arbitrage portfolio T=1 CF1 Deliver: +F Payoff debt: -(S-I)e rT Profit = F – (S-I)e rT

12 When an Investment Asset Provides a Known Yield F 0 = S 0 e (r–q )T where q is the average yield during the life of the contract (expressed with continuous compounding)

13 Forward vs Futures Prices Forward and futures prices are usually assumed to be the same. When interest rates are uncertain they are, in theory, slightly different: A strong positive correlation between interest rates and the asset price implies the futures price is slightly higher than the forward price A strong negative correlation implies the reverse

14 Stock Index Can be viewed as an investment asset paying a dividend yield The futures price and spot price relationship is therefore F 0 = S 0 e (r–q )T where q is the dividend yield on the portfolio represented by the index

15 Stock Index (continued) For the formula to be true it is important that the index represent an investment asset In other words, changes in the index must correspond to changes in the value of a tradable portfolio The Nikkei index viewed as a dollar number does not represent an investment asset

16 Index Arbitrage When F 0 >S 0 e (r-q)T an arbitrageur buys the stocks underlying the index and sells futures When F 0 <S 0 e (r-q)T an arbitrageur buys futures and shorts or sells the stocks underlying the index

17 Index Arbitrage (continued) Index arbitrage involves simultaneous trades in futures and many different stocks Very often a computer is used to generate the trades Occasionally (e.g., on Black Monday) simultaneous trades are not possible and the theoretical no-arbitrage relationship between F 0 and S 0 does not hold

18 A foreign currency is analogous to a security providing a dividend yield The continuous dividend yield is the foreign risk-free interest rate It follows that if r f is the foreign risk-free interest rate Futures and Forwards on Currencies

19 Suppose F > Se (r-r f )T Let S be the spot exchange rate in $/£ Then S dollars buys 1 pound Alternative to forward is to convert dollars to pounds and then invest in Britain Therefore, carry cost in domestic currency is offset by foreign currency rate q = r f

20 Borrow $S exchange £1 £ e r f T invest $ Se rT $/£ Se (r-r f )T repay

21 Futures on Consumption Assets F 0  S 0 e (r+u )T where u is the storage cost per unit time as a percent of the asset value. Alternatively, F 0  (S 0 +U )e rT where U is the present value of the storage costs.

22 The Cost of Carry The cost of carry, c, is the storage cost plus the interest costs less the income earned For an investment asset F 0 = S 0 e cT For a consumption asset F 0  S 0 e cT The convenience yield on the consumption asset, y, is defined so that F 0 = S 0 e (c–y )T