Robabeh Eslami - Department of Mathematics, Faculty of Basic Science, South Tehran Branch, Islamic Azad University, Tehran, Iran
Mohammad Khoveyni - Department of Applied Mathematics, College of Basic Sciences, Yadegar-e-Imam Khomeini (RAH) Branch, Islamic Azad University, Tehran, Iran
Zeynab Alihosseini - Department of Mathematics, Faculty of Basic Science, South Tehran Branch, Islamic Azad University, Tehran, Iran

This research theoretically explores estimating right and left returns to scales (RTSs) of efficient decision making units (DMUs) using hyperplanes in data envelopment analysis. In this current study, we propose a multiplier model approach for determining the type of right and left returns to scales of efficient DMUs.The important advantage of our proposed approach is that our approach is always feasible for all DMUs under assessment while Golany and Yu’s RTS method is not always feasible. It is necessary to mention that, since an inefficient decision making unit (DMU) has more than one projection on the empirical function thus different types of right and left returns to scales can be obtained for projections of the inefficient DMU, using our proposed method. At last, our approach is applied to real world data set to illustrate purpose and then some conclusions are drawn.

Data envelopment analysis (DEA), Right and left returns to scales (RTSs), Efficiency