DEA is a decision making tool based on LPP for estimating the relative efficiencies of a group of comparable units. Data Envelopment Analysis has strong connection with theory of production in Econometrics and it is often applied for benchmarking in operational management problems. In this research article a classification of efficiency stability regions has been proposed and their infeasibilities are presented. The main purpose of this article is to investigate how robust is the efficiency of an extremely efficient Decision Making Unit (DMU). Input oriented super efficiency problems of DMU have been solved in this article in order to examine how robust an extremely efficient DMU is for increases of inputs. © IJSTR 2020.