Credit card interest rates are influenced by the Federal Reserve’s prime rate, and the prime rate changes based on the judgment of federal regulators. Such decisions are largely based on the state of the national economy. If you have an outstanding balance on your credit card, or you tend to carry a balance from month to month, falling interest rates can be welcome news. However, the only sure way to reduce the cost of credit card interest is to avoid it altogether by paying your entire balance each month.