The biggest economic threat to bonds is rising interest rates. If you own a bond and interest rates go up, the value of your bond on the open market, with few exceptions, will go down.
Of course, if you plan to hold the bond to maturity the value of your bond doesnt change because interest rates change. Youll still get the amount promise when you bought the bond, all other things being equal.
However, if you plan to own bonds for investment purposes - that is you buy and sell bonds as you would stocks - then interest rates are very important.
Bond PricesBond prices move inversely to interest rates. When interest rates go up, bond prices go down and when interest rates go down, bond prices go up. Remember, were talking about previously issued bonds trading on the open market.
The inverse relationship is easy to see with this simple illustration.
A bond is issued for $10,000 for five years with a 5% coupon or interest rate, paid every six months. Then interest rates rise to 6%.
If you want to sell this bond, who would buy it when it is paying 1% below market rates (5% vs. 6%)? You have to sweeten the deal so the buyer gets a market rate for the bond.
You cant change the interest rate on the bond. Thats fixed at 5%. You can, however change the price you will take for the bond.
The annual payment of $500 ($10,000 x 5%) must equal a 6% payment. Doing the math, you discover that the face value of the bond must be discounted to $8,333 so that the $500 fixed payment equals a 6% yield on the buyers investment ($8,333 x 6% = $500).
If interest rates went down instead of up, you could then sell your bond at a premium over face value because the fixed interest rate would be higher than the market rate.
IllustrationPLEASE NOTE: This is just an example to illustrate the relationship between interest rates and bond prices. It does not represent an actual computation. To do this calculation correctly would require a more complicated process and the answer would be different. However, the seller would still have to discount the face value of the bond to compensate for the interest rate difference.
As I noted above, none of this matters if you plan to hold the bond to maturity. Changing interest rates have no effect on existing bonds unless you plan to buy or sell them in the open market.