Lecture 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 is 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.
Slide 8.15 Computing Yield to Maturity
Slide 8.16 YTM with Annual Coupons
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 for a lower yield.
Slide 8.17 YTM with Semiannual Coupons
Slide 8.18 Current Yield vs. Yield to Maturity
Slide 8.19 Bond Pricing Theorems
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.