Nasim Nasrabadi - Department of Mathematics, Faculty of Mathematical science and Statistics,University of Birjand , Birjand., Iran.
Sheyda Ayati - Department of Mathematics, Faculty of Mathematical science and Statistics,University of Birjand, Birjand , Iran.

In the literature of Data Envelopment Analysis (DEA), there exist several approaches for ranking efficient Decision-Making Units (DMUs). The concept of super efficiency is considered as one of the most well-known ranking methods in DEA. In this paper, a new model for ranking efficient units is formulated based on the concept supporting hyperplane of the production possibility set at the efficient unit under evaluation. in order to rank order the unit under evaluation (DMUo) , we try to find optimal hyperplane among all such hyper-planes, such that the average of its distance to all other units is minimized. In fact, the smaller the average distance of an efficient unit compared to other(inefficient) units, it means that the inefficient units need less effort to have the same performance as the efficient unit and vice versa. The proposed model is described in more detail in the third part of the article, then illustrated by a numerical example.

data envelopment analysis, Super efficiency, Ranking of efficient units