Discounted Present Value

At higher interest rates, firms are less likely to borrow for investment projects, and households are less likely to borrow to purchase housing and durable goods such as new cars. Thus spending on durable goods is lower at higher interest rates and vice versa. Discounted Present Value and Spending on Durable Goods To understand in more detail why interest rates affect spending on durable goods, consider the purchase of a machine by a firm. Firms carry out such investment spending because they expect the machine to yield a flow of profits not only in the present but also for several years into the future. A machine is a capital good; it is used in the production of other goods and is not used up during the production process. The fact that the returns from the machine accrue over several years is what we mean by the term durable. It is not correct to simply add profit flows in different years because a dollar today is usually worth more than a dollar next year. Why? If you take a dollar today and put it in a savings account at the bank, you will get your dollar plus interest back next year. If the interest rate is 10 percent, then $1 this year is worth $1.10 next year. Turning it around, $1 next year is worth only about 91 cents this year (because 1/1.1 = 0.91). The technique for adding together flows of resources in different periods is calleddiscounted present value. To work out whether a given investment is profitable, a firm must calculate the value, in today’s terms, of the flows of profits that it expects to receive. It then compares this to the cost of the investment. If the discounted present value of the profits exceeds the cost, the firm will undertake the investment.