Review on the Proportional Method of Bidirectional Compositor

This paper reviews on the proportional method of bidirectional compositor of the project selection method under constraints. Firstly this paper explains the economic meaning of the internal rate of return and thinks it doesn´t express the rate of return of unit investment and can´t be used as the concept of marginal revenue so the theory foundation of the method is wrong. And then it analyzes the specific applicable scope of the method that scholars in China never pay attention to when introducing and using it. Finally through the validity proof this paper thinks the proportional method of bidirectional compositor is essentially NPVR ranking method in the special condition. This method has a limited applicable scope and has not good use effect and in the practical application only can be used as an approximate method.