Ranking Efficient Decision Making Units in Data Envelopment Analysis based on Changing Reference Set

One of the drawbacks of Data Envelopment Analysis (DEA) is the problem of lack of discrimination among efficient Decision Making Units (DMUs). A method for removing this difficulty is called changing reference set proposed by Jahanshahloo and et.al (2007). The method has some drawbacks. In this paper a modified method and new method to overcome these problems are suggested. The main advantage of this method is minimizing coefficient of variation t that has crucial role in ranking efficient DMUs. Numerical example for illustration suggested method are given. To validate new methods, the author compared the obtained result from new suggested method with Norm 1 which is efficient methods for ranking DMus.