Should you invest in U.S. bonds? Part 2

Sources and types of risk in U.S. and other bonds.

This is part 2 of a multipart [Part One is here, Ed.] series on the factors that drive U.S. and foreign bond prices and yields.

Recall that a bond’s price is the present value of its coupons (if any) and face value (or principal or par value).  Let’s keep things simple for now and assume a zero-coupon or “discount” bond.

One thing of interest to note first: As we move forward in time from the issue date toward the maturity date, and the number of periods between now and the maturity date falls, the price of a discount bond rises toward the face value of the bond, even with no changes in the interest rate.  At maturity, the price of the bond equals the face value. Only unexpected changes in the effective return on a bond can change the natural upward progression of its price toward face value between the issue and maturity dates.

This example makes clear that the (annual) yield on a bond, simply put, is driven by the difference between the price paid for the bond and the cash flows it generates, that is, the difference between “dollars out” today and “dollars in” later.

The “dollars out” are known because we pay a given price for the bond today.  The “dollars in,” consisting of coupons (if any) and the face value of the bond, are also “known” in that they are specified in a contract at the time the bond is issued.  The realized value of these dollar returns is, however, subject to many different sources of uncertainty or risk. A short list includes:

Interest rate risk: how sensitive the price of the bond is to changes in interest rates over the life of the bond.  Interest rate risk is higher for bonds with a longer maturity (more time for the unexpected to happen), a lower coupon (more of the value of the bond is tied up in the principal), and a lower initial yield (a 1 percentage point change in interest rates represents a higher relative change in low yields).  Floating-rate notes and bonds have much lower, though not zero, interest rate risk.

Reinvestment rate risk.  Bondholders may reinvest their coupons at the then-prevailing rate of interest. As those market rates of interest change, the return on reinvested coupons becomes more uncertain. The higher the coupons, the more frequently they are paid, and the longer the maturity of the bond, the higher reinvestment rate risk.

Bankruptcy Court: Destination for issuers in default

Credit or default risk:  the risk that the issuer will default on the payments of the bond, which reduces the amount and value of “dollars in” relative to price paid, lowering the earned yield on the bond.   Credit risk is frequently measured as the credit spread over like Treasuries, which are assumed to have zero credit risk.  Credit risk includes downgrade risk, where a credit rating agency lowers the rating on an issuer as their ability to repay the debt is brought into question.

Call risk:  the risk that a callable bond will be called by the issuer. Since a bond is typically called only when it’s in the best interest of the issuer, the call feature is systematically harmful to the bondholder.  Prepayment risk reverses these risks:  prepayment is good for the bondholder, and bad for the issuer.

Exchange rate risk (that the value of the repaid currency will be lower), inflation risk (that the value of the repaid dollar will be lower), and event risk (natural disasters, corporate restructurings, regulatory changes, sovereign or political changes) round out the list of broad types of risks that drive bond yields.

Next time: why the types and level of risks are so difficult to measure and predict.

by Sherry Jarrell

2 thoughts on “Should you invest in U.S. bonds? Part 2

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