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如果你总和别人比，你会过得很苦。如果你不断和现在的自己比，那你会变得更好!
If you continuously compete with others, you become bitter.
If you continuously compete with yourself,you become better.净现值
Net present Value
在许多分析现金流的场合下，净现值NPV与内部回报率IRR是两个反复被使用的概念，其中，最常见的运用就是资本运算（Capital Budgeting）.资本预算是指公司在长期项目与投资之间进行资金分配，这涉及比较不同项目或投资的未来现金流。比较不同项目现金流有两种基本方法，即净现值与内部回报率法。
In many cases of cash flow analysis, NPV and IRR are two frequently used concepts, among which capital operation is the most common one. Capital budgeting refers to the allocation of funds between long-term projects and investments, which involves comparing future cash flows of different projects or investments. There are two basic methods to compare cash flows of different projects, namely, net present value and internal rate of return.
净现值NPV是指未来现金流入现值与流出现值之间的差额。利用NPV法则判断是否应该投资一个项目包括以下五个步骤：
（1）确定项目未来所有的现金流（同时包括现金流流出与流入）
（2）确定项目现金流的折现率或机会成本R
（3）利用折现率，计算出所有现金流的现值（现金流流入用正好表示，提升NPV值；反之流出用负号表示，降低NPV值）。
（4）将所有现金流现值加总，即可得NPV值
（5）利用NPV法则进行判断：若该项目NPV值为正数，则该项目可以投资；反之，若NPV为负数，则该项目不能投资，如果投资者只能在两个备选项目中投资一个（Mutually exclusive project ）,投资者应当选择NPV 较大的项目
NPV refers to the difference between the present value of future cash inflows and the present value of outflows. Using NPV rule to determine whether a project should be invested includes the following five steps:
(1)Determine all future cash flows of the project (including both outflows and inflows)
(2)Determining the discount rate or opportunity cost R of project cash flow
(3) Using the discount rate, the present value of all cash flows is calculated (cash inflows are represented by positive signs to increase NPV value, where as outflows are represented by negative signs to reduce NPV value).
(4) NPV can be obtained by summing up all cash flow present values.
(5) Use NPV rule to judge: if the NPV value of the project is positive, then the project can be invested; otherwise, if the NPV is negative, then the project can not be invested. If the investor can only invest in one of the two alternative projects, the investor should choose the project with larger NPV.
NPV公式（formula）
tips: ∑公式计算：表示起和止的数。比如说下面t=0,N=3，表示从0起到3止的和。
Formula calculation: Number indicating beginning and ending. For example, let's say t = 0, N = 3, which means the sum from 0 to 3.
其中CFt 表示第T期的现金流，N表示项目持续时间、r表示资金的折现率或机会成本。
资金的机会成本r指如果资金没有投资该项目，而是进行其他投资可以获得的收益率。
换言之，r表示了投资该项目，投资者期望的最低收益率。因此，如果按此贴现率计算出的NPV为正，表明该项目增加了股东财富；反之则减少了股东财富。
Among them, CFt represents the cash flow of the T period, N represents the duration of the project, R represents the discount rate or opportunity cost of the fund.
Opportunity cost r of funds refers to the rate of return that can be obtained if the funds do not invest in the project but make other investments.
In other words, R represents the lowest rate of return expected by investors when investing in the project. Therefore, if the NPV calculated at this discount rate is positive, it shows that the project increases share holder wealth; on the contrary, it decreases shareholder wealth.
例题
某项目需要在期初投入研发成本200万元，项目持续3年，预计分别能在第一年、第二年与第三年末收到50万元、75万元、与135万元。如果折现率为10%，该项目是否值得投资？
Example
A project needs to invest 2 million yuan in research and development cost at the beginning of the period and lasts for three years. It is expected to receive 500,000 yuan, 750,000 yuan and 1.35 million yuan in the first year, the second year and the end of the third year, respectively. If the discount rate is 10%,is the project worth investing?
解析
直接带入NPV 公式计算即可。
净现值=未来现金流入现值与流出现值之间的差额
NPV=-200（流出现值）+50/（1+10%）+75/（1+10%）2+135/（1+10%）3=8.7
NPV大于零，因此该项目值得投资
analysis
The NPV formula can be calculated directly.
Net present value = the difference between the present value of future cash inflows and the present value of cash outflows
NPV=-200（outflow present value）+50/（1+10%）+75/（1+10%）2+135/（1+10%）3=8.7
NPV is greater than zero, so the project is worth investing.
