技术经济学英文版演示文稿C2.pptVIP

(2.28) Note that if compounding sub-periods, M, is equal to one, then, Example 2.20 A bank advertises in a newspaper: “Invest a minimum of $5,000 today in a CD (Certificate of Deposit) account at an interest rate of 8.5% per year and receive an effective yield of 8.87% per year by compounding the interest daily.” Do you believe that this statement is accurate? Solution Given: j = 8.5% per year, M = 365 (365 sub-periods in one year) Find: i Using Eq. 2.28, The effective interest rate is 8.87%. Therefore, the statement is accurate. Example 2.21 A credit card agreement states that“ The finance charge will be calculated on a monthly basis based on the Average Daily Balance.” Further it states that the finance charge is“ l.75% which is an ANNUAL PERCENTAGE RATE OF 21%.”Is this an accurate statement? Solution The finance charge is calculated on a monthly basis. If we assume that the nominal interest rate per year is 21%, then the monthly nominal interest rate is, using Eq.2.25. Therefore, the statement in the credit card is accurate to the extent that 21% is the Nominal annual percentage rate. However, the interest is compound monthly. Therefore, M is equal to 12. Using Eq. 2.28, The effective interest rate is 23.14%, which is much greater than 21% as advertised. We, therefore, can say that the statement in the agreement is misleading(令人误解的) because it does not specify whether the interest is nominal or effective. In defining the time value of money, we should use the effective interest rate rather than the nominal interest rate in our computations. The effective interest rate is the actual interest rate charged to the principal. In applying any of the equations we learned in the previous section, it should be remembered that the units for many of the terms should be consistent. The determining factor in most instances is the periodic payment. The interest rate used in any calculation should be the effective interest rate per period