This post was originally made on July 27, 2006 on a former blog of mine.
Some people get confused between the coupon rate and yield of a bond so I wanted to go over some bond basics to sort of clear things up. The value of a bond is made up of several parts:
- Par Value - this is the original face value of the bond. Most bonds have a par value of $1000 but there are some that are different.
- Coupon Rate - this is the percentage used to determine the yearly payment based on the par value of the bond. If the coupon rate is 8% on a $1000 bond then you will get paid $80 per year until the bond matures.
- Time to Maturity - this is the amount of time remaining until the bond matures, basically, this is when you will receive the par value of the bond back in addition to the final coupon payment. If a 30 year bond has 25 years left, its time to maturity is 25.
- Current Prevailing Interest Rates - this is key because people are not going to buy bonds paying 5% if the current market interest rates on similar products is 7%.
Since the Coupon Rate, Par Value, and Duration of the bond are all fixed, the only thing that can change in the market is the price someone is willing to pay for that stream of cash flows. Just because someone paid $1000 for a $1000 8% 10 year bond today does not mean that the same bond will fetch $1000 in today’s market. It may trade above or below that amount depending upon the prevailing interest rates in relation to the coupon payment.
The way one determines how much a bond is worth is by setting the needed interest rate to whatever the prevailing market rates of the day are (also called Yield to Maturity) and then recalculating the bond price (you can use a financial calculator or Excel if you want).
Here is an example. Suppose you have a 30 year bond, $1000 par value, and its coupon payment is 5% (or $50 annual payments). If the current market interest rates were 5% then this bond would trade at its par value of $1000. If, however, rates were to rise then this is what would happen:
Suppose one year later interest rates were at 7% instead of 5%. This means in order for someone to want this stream of cash flows the yield on the bond would have to be at least equivalent to the current interest rates. Therefore we must pay LESS than par value for the bond in order for the rates to make it worth while. This is called trading at a discount.
If you set your calculator to FV=1000 (you get paid the 1000 par no matter how much you pay for the bond if you hold it to maturity), N=29 (29 yrs left to maturity since we are one year later than the original 30 year issue date), PMT=50 (the payment does not change, it will always be $50 or the original coupon rate times the original par value), and I/YR=7 (this is the NEW INTEREST RATE you require - NOT the coupon rate!!!). Then hit the PV (present value) button and you will get $754.45. This is how much the bond should now be trading for with 7% market interest rates. Note: in an Excel spreadsheet you could use the following formula =PV(0.07,29,50,1000).
It is also possible for bonds to trade at a premium, or above their par value. This happens when the present market interest rates are BELOW the coupon rate on the bond. People are then willing to pay more for that stream of cash flows. There are also callable bonds, which means the issuer can call them away before the maturity date. Valuing callable bonds is something I do not want to get into today.
So, there is your little basic primer on bond valuation. It’s not that difficult but all the different uses of percentages can be confusing. Just remember the Coupon Rate is fixed when the bond is originally issued and always simply reflects the payment amount based on the original par value of the bond. The Yield to Maturity (aka interest rate, yield) is the present rate required in order for someone to actually want to purchase the bond in the open market at this time.
“The Great Inflation of the 1970s destroyed faith in paper assets, because if you held a bond, suddenly the bond was worth much less money than it was before.” -Ron Chernow
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