Effective yield is a financial metric that measures the interest rate – also known as the coupon rate – return on a bond. The effective yield metric is that it takes compounding into consideration.
It is important because bonds typically pay interest more than once a year. It makes effective yield a more accurate investment return metric than the nominal, or simple, yield metric, which does not take the effect of compounding into account.
However, one drawback of the effective yield metric is that it assumes that the investor – the bondholder – can reinvest the interest payments they receive at the same rate as the stated coupon rate on their bond.
For example, if an investor purchases a bond that pays a 7% coupon rate, the effective yield calculation assumes that the investor can reinvest all the 7% interest payments they receive in another bond or similar investment that will also provide an ongoing 7% return.
Since interest rates are constantly fluctuating, the above is an unlikely scenario. In an economic environment where interest rates are declining, reinvesting at the same interest rate as that received on a previously purchased bond is virtually impossible.
Effective yield is an investment return metric that reflects the interest payments received and the effect of compounding on an investment.
A key assumption of the effective yield metric is that coupon payments received on a bond can be reinvested at the same interest rate as the bond’s nominal (stated) interest rate – an assumption that may or may not be valid.
The effective yield metric is often contrasted with the nominal yield metric, or with the bond equivalent yield, a measure that is applied to zero-coupon bonds.
Formula for Calculating the Effective Yield
The formula for calculating the effective yield on a bond purchased:
Effective Yield = [1 + (i/n)]n – 1
i – The nominal interest rate on the bond
n – The number of coupon payments received in each year
Assume that you purchase a bond with a nominal coupon rate of 7%. Coupon payments are received, as is common with many bonds, twice a year.
Plugging in the calculation formula, you calculate the yield as follows:
[1 + (.07/2)]2 – 1 = 7.123%
To see how the number of annual coupon payments received affects the effective yield on your bond, let us do another effective yield calculation that assumes you receive monthly coupon payments – 12 interest payments each year.
With 12 monthly coupon payments, the calculation formula would be as follows:
[1 + (.07/12)]12 – 1 = 7.229%
The higher resulting effective yield clearly shows the benefit for investors of more frequent compounding of interest.
Doing an effective yield calculation can be of value to an investor who is comparing two bonds with different coupon rates and different compounding periods.
Effective Yield vs. Bond Equivalent Yield
The effective yield metric measures the investment return earned through the coupon payments received from a bond.
It is not the same as the metric known as the bond equivalent yield, which is an investment return metric based solely on the face value – or par value – of the bond, which will be paid to the bondholder by the bond’s issuer when the bond reaches maturity, and the price at which the bond was purchased.
In other words, the bond equivalent yield does not take coupon payments into account. It is used to calculate the investment return on a zero-coupon bond, one that does not offer coupon payments other than the interest earned at the time the bond reaches maturity and is redeemed by the issuer.
Unless you buy a bond upon its initial issue, you will rarely pay the exact par value, or face value, of the bond. Instead, you will most likely purchase the bond at either a premium or a discount to its face value.
Purchasing the bond at a premium – a price higher than the bond’s face value – will reduce your total return on the bond while purchasing the bond at a discount from face value will increase your overall return.
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