再论净现值与内部收益率非自洽性的原因

针对净现值（NPV）与内部收益率（IRR）的非自洽性问题，认为再投资收益率说并不能很好地解释NPV与IRR非自洽的原因。NPV与IRR非自洽性的原因在于两个指标之间不能保证一定存在单调递增关系，是指标定义本身决定了两者的非自洽性，而不是其他的原因。最后给出了投资项目NPV与IRR自洽性的条件，即只需保证项目NPV函数的图象大于零的部分不相交即可。

Further Discussion on the Reason of the Conflict Between NPV and IRR

In allusion to the reason of the conflict between NPV and IV, R, this paper thinks reinvestment rate theory can＇t explain it well. The reason of the conflict between NPV and IRR is that the two indexes can not always assure their monotone increasing relation and the definition formulas of two indexes themselves determine their conflict,but not other reasons. Finally the paper gives the self--consistency condition of investment projects NPV and IRR. The condition is that the NPV function images of different projects bigger than zero do not intersect.