Factors Affecting Bond Duration

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Duration is directly related to maturity and inversely related to the coupon rate and yield to maturity (YTM). Duration is approximately equal to the point in years where the investor receives half of the present value of the bond's cash flows. Therefore, the later the cash flows are received, the greater the duration.

The longer the time to maturity, the greater the duration (and vice versa). A longer-term bond pays its cash flows later than a shorter-term bond, increasing the duration. The lower the coupon rate, the greater the duration (and vice versa). A lower coupon bond pays lower annual cash flows than a higher-coupon bond and thus has less influence on duration. The lower the YTM, the higher the duration. This is because the bond's price (or present value) is inversely related to interest rates. When market yields fall, the value (or cash flow) of a bond increases without increasing the time to maturity.

Consider the purchase of an existing bond selling for $1,150. This bond has 28 years to maturity, pays a 12 percent annual coupon, and is callable in 8 years for

$1,100.