Numerous studies have shown that the cost of investing in an opportunity can be large and that investment rules that ignore the expense can lead the investor astray. The opportunity cost is highly sensitive to uncertainty over the future value of the project; as a result, new economic conditions that may affect the perceived riskiness of future cash flows can have a large impact on investment spending—much larger than, say, a change in interest rates. Viewing investment as an option puts greater emphasis on the role of risk and less emphasis on interest rates and other financial variables.