1 Introduction Efficiency, as well as productivity is an index that is often employed to measure the performance of a company, a region, an industry or even a country which is usually referred to as decision-making units (hereinafter DMU) in literatures.Economic efficiency or X-efficiency is the product of technical efficiency and allocative efficiency, with the former referring to the ability to produce as much output as technology and input usage allow or to use as little input as required by technology and output production, and the latter referring to the extent to which a firm uses the inputs in the best proportions,given their prices Particularly, with respect to frequently used technical efficiency, Koopmans (1951)defined it as the status in which an increase in any output of a DUM requires a reduction in at least one other output or an increase in at least one input, and if a reduction in any input requires an increase in at least one other input or a reduction in at least one output.Consequently, a technically inefficient DMU could produce the same outputs with less of at least one input that is really used, or could use the really employed inputs to produce more of at least one output if this DUM had operated as efficient as technically efficient DUM (s).