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What Is Bond Equivalent Yield

Bond equivalent yield (BEY) is a standardized way to compare the yields of different bonds, particularly those with maturities less than a year, like Treasury Bills (T-Bills). Since T-Bills are sold at a discount to their face value and don't pay periodic interest, their yield is calculated based on the difference between the purchase price and the face value, rather than through a coupon rate.

BEY converts this discount yield into an annualized rate, which is comparable to the yield on bonds that make regular interest payments. The formula for BEY takes into account the price difference, the face value, and the number of days to maturity. By using BEY, investors can easily compare the returns offered by different money market instruments, regardless of their maturity or payment structure.

For example, a T-Bill with a face value of $1,000 and a purchase price of $995 maturing in 90 days would have a discount yield of 0.5%. However, to compare this with a bond offering a 5% coupon, we need to convert the discount yield into BEY. This is done by calculating the annualized return, considering the 90-day maturity period and the 360-day year convention used in bond markets. This resulting BEY would be higher than the 0.5% discount yield, allowing for a fair comparison with other investments.

What is the Difference Between Bond Equivalent Yield and Effective Annual Yield?

Bond equivalent yield (BEY) and effective annual yield (EAY) are both measures of return on an investment, but they differ in how they account for the compounding of interest. BEY is a widely used convention for quoting the yield on fixed-income securities, like bonds, that make periodic interest payments. The formula for BEY is:

BEY = (Face Value - Purchase Price) / Purchase Price x (365 / Days to Maturity)


  • Face Value = The par value or principal amount that will be paid to the bondholder at maturity.
  • Purchase Price = The price at which the bond is purchased.
  • Days to Maturity = The number of days remaining until the bond matures.

EAY, on the other hand, considers the effect of compounding interest. It calculates the actual return an investor receives by taking into account the reinvestment of interest payments. The formula for EAY is:

EAY = (1 + r/n)^n - 1


r = nominal annual interest rate (stated rate)

n = number of compounding periods per year

BEY provides a standardized way to compare yields across different bonds, while EAY reflects the true return an investor receives over a year, considering the impact of compounding. EAY will always be higher than BEY because it accounts for the reinvestment of interest, leading to exponential growth. The difference between the two yields becomes more significant as the frequency of compounding increases.

Why is Bond Equivalent Yield Used?

The Bond Equivalent Yield (BEY) is a standardized measure used to compare the yields of different debt securities, particularly those with maturities shorter than a year. It is essential for investors and analysts as it allows for a fair comparison of returns even if the securities have different coupon frequencies or maturities.

The primary reason for using BEY is its ability to annualize yields on short-term securities, which often pay interest at a frequency higher than annually. This conversion to an annualized rate makes it easier to compare returns across investments with different payment schedules. For example, a Treasury bill with a 3-month maturity and a yield of 2% can be compared to a 6-month bond with a 3% yield, even though their interest payment periods differ.

Furthermore, BEY simplifies the calculation of returns on money market instruments. These instruments often have maturities of less than one year, making it impractical to calculate yields based on a full year. BEY provides a standardized measure that is easily understandable and allows for quick comparisons between different investments.

When is Bond Equivalent Yield Most Important?

Bond Equivalent Yield (BEY) is a crucial metric when comparing the returns of investments with different maturities, particularly those with a maturity of less than a year. It's especially essential when comparing short-term debt instruments like Treasury Bills (T-Bills) with other investments, such as money market accounts or certificates of deposit (CDs).

BEY is important because it standardizes the yield calculation for investments with different compounding frequencies. T-Bills are typically quoted on a discount basis, meaning their yield is calculated based on the difference between the purchase price and face value. However, BEY converts this discount yield into an annualized yield assuming semi-annual compounding. This makes it easier to compare T-Bills with other investments that use a standard annualized rate with semi-annual compounding.

Moreover, BEY is crucial for investors who need to make quick, informed decisions about their short-term investments. By converting yields to a common basis, BEY allows investors to efficiently compare different investment options and choose the one with the most attractive return. This is particularly valuable for institutions with large cash reserves and a need to manage their liquidity effectively.

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