Bond prices fluctuate with changing market sentiments and economic environments, but bond prices are affected in a much different way than stocks. Risks such as rising interest rates and economic stimulus policies have an effect on both stocks and bonds, but each reacts in an opposite way.

Stocks versus Bonds

When stocks are on the rise, investors generally move out of bonds and flock to the booming stock market. When the stock market corrects, as it inevitably does, or when severe economic problems ensue, investors seek the safety of bonds. As with any free-market economy, bond prices are affected by supply and demand.

Bonds are issued initially par value value, or $100. In the secondary market, a bond's price can fluctuate. The most influential factors that affect a bond's price are yield, prevailing interest rates and the bond's rating. Essentially, a bond's yield is the present value of its cash flows, which are equal to the principal amount plus all the remaining coupons.

Understanding Yield

The yield is the discount rate of the cash flows. Therefore, a bond's price reflects the value of the yield left within the bond. The higher the coupon total remaining, the higher the price. A bond with a yield of 2% likely has a lower price than a bond yielding 5%. The term of the bond further influences these effects.

For example, a bond with a longer maturity typically requires a higher discount rate on the cash flows, as there is increased risk over a longer term for debt. Also, callable bonds have a separate calculation for yield to the call day using a different discount rate. Yield to call is calculated quite differently than yield to maturity, as there is uncertainty as to when the repayment of principal and the end to coupons occurs.

Changes in Interest Rates, Inflation, and Credit Ratings

Changes in interest rates affect bond prices by influencing the discount rate. Inflation produces higher interest rates, which in turn requires a higher discount rate, thereby decreasing a bond's price. Bonds with a longer maturity see a more drastic lowering in price in this event because, additionally, these bonds face inflation and interest rate risks over a longer period of time, increasing the discount rate needed to value the future cash flows. Meanwhile, falling interest rates cause bond yields to also fall, thereby increasing a bond's price.

Credit risk also contributes to a bond's price. Bonds are rated by independent credit rating agencies such as Moody's, Standard & Poor's and Fitch to rank a bond's risk for default. Bonds with higher risk and lower credit ratings are considered speculative and come with higher yields and lower prices. If a credit rating agency lowers a particular bond's rating to reflect more risk, the bond's yield must increase and its price should drop.