Chapter 07 – Interest Rates and Bond Valuation
Real-World Tip: Upon learning the concept of interest rate risk,
students sometimes conclude that bonds with low interest-rate risk
(i.e. high coupon bonds) are necessarily “safer” than otherwise
identical bonds with lower coupons. In reality, the contrary may be
true: increasing interest rate volatility over the last two decades
has greatly increased the importance of interest rate risk in bond
valuation. The days when bonds represented a “widows and
orphans” investment are long gone.
You may wish to point out that one potentially undesirable feature
of high-coupon bonds is the required reinvestment of coupons at
the computed yield-to-maturity if one is to actually earn that yield.
Those who purchased bonds in the early 1980s (when even high-
grade corporate bonds had coupons over 11%) found, to their
dismay, that interest payments could not be reinvested at similar
rates a few years later without taking greater risk. A good example
of the trade-off between interest rate risk and reinvestment risk is
the purchase of a zero-coupon bond – one eliminates reinvestment
risk but maximizes interest-rate risk.
D. Finding the Yield to Maturity: More Trial and Error
It is a trial and error process to find the YTM via the general
formula above. Knowing if a bond sells at a discount (YTM >
coupon rate) or premium (YTM < coupon rate) is a help, but using
a financial calculator is by far the quickest, easiest, and most
accurate method.
Lecture Tip: Students should understand that finding the yield to
maturity is a tedious process of trial and error. It may help to pose
a hypothetical situation in which a 10-year, 10% coupon bond
sells for $1,100. Ask whether paying a higher price than $1,000
would yield an investor more or less than 10%. Hopefully, the
students will recognize that if they pay $1,000 for the right to
receive $100 per year, the bond would yield 10%. Thus a starting
point in determining the YTM would be 9%. And if the same bond
is selling for $1,200, one might want to try 8% as a starting point,
since we would be paying a higher price and earning a lower
yield.
Lecture Tip: You may wish to discuss the components of required
returns for bonds in a fashion analogous to the stock return
discussion in the next chapter. As with common stocks, the required
return on a bond can be decomposed into current income and
capital gains components. The yield-to-maturity (YTM) equals the
current yield plus the capital gains yield.
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