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Chapter. 9. Interest Rate Risk II. Overview. This chapter discusses a market value-based model for assessing and managing interest rate risk: Duration Computation of duration Economic interpretation Immunization using duration * Problems in applying duration.
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Chapter 9 Interest Rate Risk II
Overview • This chapter discusses a market value-based model for assessing and managing interest rate risk: • Duration • Computation of duration • Economic interpretation • Immunization using duration • * Problems in applying duration
Price Sensitivity and Maturity • In general, the longer the term to maturity, the greater the sensitivity to interest rate changes. • Example: Suppose the zero coupon yield curve is flat at 12%. Bond A pays $1762.34 in five years. Bond B pays $3105.85 in ten years, and both are currently priced at $1000.
Example continued... • Bond A: P = $1000 = $1762.34/(1.12)5 • Bond B: P = $1000 = $3105.84/(1.12)10 • Now suppose the interest rate increases by 1%. • Bond A: P = $1762.34/(1.13)5 = $956.53 • Bond B: P = $3105.84/(1.13)10 = $914.94 • The longer maturity bond has the greater drop in price because the payment is discounted a greater number of times.
Coupon Effect • Bonds with identical maturities will respond differently to interest rate changes when the coupons differ. This is more readily understood by recognizing that coupon bonds consist of a bundle of “zero-coupon” bonds. With higher coupons, more of the bond’s value is generated by cash flows which take place sooner in time. Consequently, less sensitive to changes in R.
Remarks on Preceding Slides • The longer maturity bonds experience greater price changes in response to any change in the discount rate. • The range of prices is greater when the coupon is lower. • The 6% bond shows greater changes in price in response to a 2% change than the 8% bond. The first bond is has greater interest rate risk.
Duration • Duration • Weighted average time to maturity using the relative present values of the cash flows as weights. • Combines the effects of differences in coupon rates and differences in maturity. • Based on elasticity of bond price with respect to interest rate.
Duration • Duration D = Snt=1[Ct• t/(1+r)t]/ Snt=1 [Ct/(1+r)t] Where D = duration t = number of periods in the future Ct = cash flow to be delivered in t periods n= term-to-maturity & r = yield to maturity (per period basis).
Duration • Since the price of the bond must equal the present value of all its cash flows, we can state the duration formula another way: D = Snt=1[t (Present Value of Ct/Price)] • Notice that the weights correspond to the relative present values of the cash flows.
Duration of Zero-coupon Bond • For a zero coupon bond, duration equals maturity since 100% of its present value is generated by the payment of the face value, at maturity. • For all other bonds: • duration < maturity
Computing duration • Consider a 2-year, 8% coupon bond, with a face value of $1,000 and yield-to-maturity of 12%. Coupons are paid semi-annually. • Therefore, each coupon payment is $40 and the per period YTM is (1/2) × 12% = 6%. • Present value of each cash flow equals CFt ÷ (1+ 0.06)t where t is the period number.
Special Case • Maturity of a consol: M = . • Duration of a consol: D = 1 + 1/R
Duration Gap • Suppose the bond in the previous example is the only loan asset (L) of an FI, funded by a 2-year certificate of deposit (D). • Maturity gap: ML - MD = 2 -2 = 0 • Duration Gap: DL - DD = 1.885 - 2.0 = -0.115 • Deposit has greater interest rate sensitivity than the loan, so DGAP is negative. • FI exposed to rising interest rates.
Features of Duration • Duration and maturity: • D increases with M, but at a decreasing rate. • Duration and yield-to-maturity: • D decreases as yield increases. • Duration and coupon interest: • D decreases as coupon increases
Economic Interpretation • Duration is a measure of interest rate sensitivity or elasticity of a liability or asset: [dP/P] [dR/(1+R)] = -D Or equivalently, dP/P = -D[dR/(1+R)] = -MD × dR where MD is modified duration.
Economic Interpretation • To estimate the change in price, we can rewrite this as: dP = -D[dR/(1+R)]P = -(MD) × (dR) × (P) • Note the direct linear relationship between dP and -D.
Semi-annual Coupon Payments • With semi-annual coupon payments: (dP/P)/(dR/R) = -D[dR/(1+(R/2)]
An example: • Consider three loan plans, all of which have maturities of 2 years. The loan amount is $1,000 and the current interest rate is 3%. Loan #1, is an installment loan with two equal payments of $522.61. Loan #2 is a discount loan, which has a single payment of $1,060.90. Loan #3 is structured as a 3% annual coupon bond.
Immunizing theBalance Sheet of an FI • Duration Gap: • From the balance sheet, E=A-L. Therefore, DE=DA-DL. In the same manner used to determine the change in bond prices, we can find the change in value of equity using duration. • DE = [-DAA + DLL] DR/(1+R) or • DE = -[DA - DLk]A(DR/(1+R))
Duration and Immunizing • The formula shows 3 effects: • Leverage adjusted D-Gap • The size of the FI • The size of the interest rate shock
An example: • Suppose DA = 5 years, DL = 3 years and rates are expected to rise from 10% to 11%. (Rates change by 1%). Also, A = 100, L = 90 and E = 10. Find change in E. • DE = -[DA - DLk]A[DR/(1+R)] = -[5 - 3(90/100)]100[.01/1.1] = - $2.09. • Methods of immunizing balance sheet. • Adjust DA , DL or k.
Immunization and Regulatory Concerns • Regulators set target ratios for a bank’s capital (net worth): • Capital (Net worth) ratio = E/A • If target is to set (E/A) = 0: • DA = DL • But, to set E = 0: • DA = kDL
*Limitations of Duration • Immunizing the entire balance sheet need not be costly. Duration can be employed in combination with hedge positions to immunize. • Immunization is a dynamic process since duration depends on instantaneous R. • Large interest rate change effects not accurately captured. • Convexity • More complex if nonparallel shift in yield curve.
*Convexity • The duration measure is a linear approximation of a non-linear function. If there are large changes in R, the approximation is much less accurate. All fixed-income securities are convex. Convexity is desirable, but greater convexity causes larger errors in the duration-based estimate of price changes.
*Convexity • Recall that duration involves only the first derivative of the price function. We can improve on the estimate using a Taylor expansion. In practice, the expansion rarely goes beyond second order (using the second derivative).
*Modified duration • DP/P = -D[DR/(1+R)] + (1/2) CX (DR)2 or DP/P = -MD DR + (1/2) CX (DR)2 • Where MD implies modified duration and CX is a measure of the curvature effect. CX = Scaling factor × [capital loss from 1bp rise in yield + capital gain from 1bp fall in yield] • Commonly used scaling factor is 108.
*Calculation of CX • Example: convexity of 8% coupon, 8% yield, six-year maturity Eurobond priced at $1,000. CX = 108[DP-/P + DP+/P] = 108[(999.53785-1,000)/1,000 + (1,000.46243-1,000)/1,000)] = 28.
*Duration Measure: Other Issues • Default risk • Floating-rate loans and bonds • Duration of demand deposits and passbook savings • Mortgage-backed securities and mortgages • Duration relationship affected by call or prepayment provisions.
*Contingent Claims • Interest rate changes also affect value of off-balance sheet claims. • Duration gap hedging strategy must include the effects on off-balance sheet items such as futures, options, swaps, caps, and other contingent claims.
Pertinent Websites Securities Exchange Commission www.sec.gov Web Surf