Bond Duration and Convexity

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Notes. Page 1. Economics of Capital Markets. Page 1. Version 1.0 Outline. Bond Duration and Convexity. Bond Duration and Convexity. Major Topics:.
Notes Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Major Topics:

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Economics of Capital Markets

Introduction Introduction

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Notes Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction „

We already know the relationship between bond prices and yields (or required rates of return) – Some others may be new

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Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction (Continued) (Continued)

1. The value of a bond is inversely related to changes in the investor’s required rate of return. –

The higher the required rate of return, the lower the bond value.

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Notes Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction (Continued) (Continued)

1. Prices and returns on bonds are inversely related $200

P0B =

Price

$150

C y

 1 F  + 1 − n (1 + y )n   (1 + y )

$100 $50 $0 0%

2%

4%

6%

8%

10%

12%

Yield

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14%

16% Page 5

Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction (Continued) (Continued)

2 The market value of a bond will be less than the par value if the investor’s required rate is above the coupon interest rate

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Notes Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction (Continued) (Continued) Premium bonds Par bonds Discount bonds

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Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction (Continued) (Continued)

Price

3. Long-term bonds have greater interest rate risk than short term bonds. $250

20

$200

10

$150

5

10 Year 20 Year 5 Year 5 10 20

$100 $50 $0 0%

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2%

4%

6%

8% Yield

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10%

12%

14%

16%

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Notes Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction (Continued) (Continued)

Corollary: Low coupon bonds have greater interest rate sensitivity than high coupon bonds.

3.

Price

$200 $150

Coupon Zero

Zero Coupon

$100

Coupon

$50

Zero

15%

13%

9% Yield

11%

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7%

5%

3%

1%

$0 Page 9

Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Introduction Introduction (Continued) (Continued) „

The sensitivity of a bond’s value to changing interest rates depends on both the length of time to maturity and on the pattern of cashflows provided by the bond

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Notes Economics of Capital Markets

Duration Duration

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Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Duration Duration „

We want to know how the price of a bond changes as the yield changes

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Notes Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Duration Duration (Continued) (Continued) „

To derive the elasticity, use n

P =∑ B 0

t =1

C F + (1 + y)t (1 + y)n

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Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Duration Duration (Continued) (Continued) „

Take the first derivative with respect to y to get

dP0B (-1)C (-2)C (-n)C (-n)F = + + + + ... dy (1 + y)2 (1 + y)3 (1 + y)n +1 (1 + y)n +1 =-

1  1C 2C nC nF  + + + + ... 1 + y  (1 + y)1 (1 + y)2 (1 + y)n (1 + y)n 

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Notes Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Duration Duration (Continued) (Continued) „

Multiplying through by 1 P0B

dP0B 1 1  1C 2C nC nF  1 =+ + ... + + ∗  B 1 2 n dy P0 1 + y  (1 + y) (1 + y) (1 + y) (1 + y)n  P0B =-

1 D 1+ y

where

 1C 2C nC nF  1 D= + + ... + + ∗ >0 1 2 n (1 + y) (1 + y)n  P0B  (1 + y) (1 + y) Version 1.0 Outline

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Economics of Capital Markets

Bond Bond Duration Duration and and Convexity Convexity Duration Duration (Continued) (Continued) „

Now we can get

dP0B 1 + y =-D