Capital appreciation: Bond prices can rise for several reasons, including a drop in interest rates and an improvement in the credit standing of the issuer. There's going to be an inverse relationship between the interest rate and bond prices if interest rates fall bond prices are going to increase.Most bonds and interest rates have an inverse relationship. So, higher interest rates mean lower prices for existing bonds. A not too mathy explanation of why bond prices, why bond prices move in the opposite direction as interest rates. If the bond price goes up, the interest rate—or cost of the loan—goes down. Supply and demand in the bond market. Bond prices fluctuate based on interest rates, credit quality and market demand. Here's what you need to know before investing. A demand for any particular bond will be 0 if its price is above the present value and infinity if it's below.