IV. CRITERIA FOR INVESTMENT SELECTION
Theory—In the above discussion of return and risk, we purposefully used the term "return" in its generic sense, without defining it as internal rate of return (IRR), net present value (NPV), payback period, or accounting profit, so that we could focus on the concept of risk. Current theory generally regards IRR, or its equivalent NPV, as a better measure of return than either
the payback period or the accounting profit. The reason for this preference is that under conditions of certainty, of two investments of equal size, tlie one which has a higher IRR results in higher value for the firm. This preference has been carried over to conditions of uncertainty without sufficient critical analysis. Both the payback period and accounting profit have been regarded as inferior, because at best they can only be used to approximate the IRR. However, since the payback period is usually justified as a method of incorporating risk, a much more pertinent criticism is the limited applicability of the payback period as a method of risk analysis. Also, since reported earnings do affect share prices, investment decisions must consider the effect on accounting profit, if the goal is to maximize share values.