什么叫内部利润率（internal rate of return，简记为IRR）？其经济含义和实际意义是什么？

参考答案：所谓外部性效应，即如果不存在利益补偿，那么一个人或企业的行为就会影响其他人的福利或其他企业的盈利能力。如果某些行为主体的行为使得其他主体的境况变好，那么外部性为正;如果这些行为使得其他主体的境况变坏，那么这种外部性就是负的。或者说，当一个人从事一种影响旁观者福利，而他对这种影响既不支付成本又得不到报酬的活动时，就产生了外部性。如果对旁观者的影响是不利的，就称为负外部性;如果这种影响是有利的，就称为正外部性。

正确答案：

正确答案：A

正确答案：
(c) There are many reasons that could be discussed in support of the view that net present value (NPV) is superior to other
investment appraisal methods.
NPV considers cash flows
This is the reason why NPV is preferred to return on capital employed (ROCE), since ROCE compares average annual
accounting profit with initial or average capital invested. Financial management always prefers cash flows to accounting profit,
since profit is seen as being open to manipulation. Furthermore, only cash flows are capable of adding to the wealth of
shareholders in the form. of increased dividends. Both internal rate of return (IRR) and Payback also consider cash flows.
NPV considers the whole of an investment project
In this respect NPV is superior to Payback, which measures the time it takes for an investment project to repay the initial
capital invested. Payback therefore considers cash flows within the payback period and ignores cash flows outside of the
payback period. If Payback is used as an investment appraisal method, projects yielding high returns outside of the payback
period will be wrongly rejected. In practice, however, it is unlikely that Payback will be used alone as an investment appraisal
method.
NPV considers the time value of money
NPV and IRR are both discounted cash flow (DCF) models which consider the time value of money, whereas ROCE and
Payback do not. Although Discounted Payback can be used to appraise investment projects, this method still suffers from the
criticism that it ignores cash flows outside of the payback period. Considering the time value of money is essential, since
otherwise cash flows occurring at different times cannot be distinguished from each other in terms of value from the
perspective of the present time.
NPV is an absolute measure of return
NPV is seen as being superior to investment appraisal methods that offer a relative measure of return, such as IRR and ROCE,
and which therefore fail to reflect the amount of the initial investment or the absolute increase in corporate value. Defenders
of IRR and ROCE respond that these methods offer a measure of return that is understandable by managers and which can
be intuitively compared with economic variables such as interest rates and inflation rates.
NPV links directly to the objective of maximising shareholders’ wealth
The NPV of an investment project represents the change in total market value that will occur if the investment project is
accepted. The increase in wealth of each shareholder can therefore be measured by the increase in the value of their
shareholding as a percentage of the overall issued share capital of the company. Other investment appraisal methods do not
have this direct link with the primary financial management objective of the company.
NPV always offers the correct investment advice
With respect to mutually exclusive projects, NPV always indicates which project should be selected in order to achieve the
maximum increase on corporate value. This is not true of IRR, which offers incorrect advice at discount rates which are less
than the internal rate of return of the incremental cash flows. This problem can be overcome by using the incremental yield
approach.
NPV can accommodate changes in the discount rate
While NPV can easily accommodate changes in the discount rate, IRR simply ignores them, since the calculated internal rate
of return is independent of the cost of capital in all time periods.
NPV has a sensible re-investment assumption
NPV assumes that intermediate cash flows are re-invested at the company’s cost of capital, which is a reasonable assumption
as the company’s cost of capital represents the average opportunity cost of the company’s providers of finance, i.e. it
represents a rate of return which exists in the real world. By contrast, IRR assumes that intermediate cash flows are reinvested
at the internal rate of return, which is not an investment rate available in practice,
NPV can accommodate non-conventional cash flows
Non-conventional cash flows exist when negative cash flows arise during the life of the project. For each change in sign there
is potentially one additional internal rate of return. With non-conventional cash flows, therefore, IRR can suffer from the
technical problem of giving multiple internal rates of return.