Evaluating the efficiency of decision making units in the presence of flexible and negative data

Looking into the literature reveals that conventional data envelopment analysis (DEA) models assume non-negative inputs and outputs in which the status of each measure is known as either input or output. However, occasions arise where a measure can play either input or output roles and can take negative values. Emrouznejad et al., (2010a) [Emrouznejad A, Anouze A.L and Thanassoulis E (2010a)A semi-oriented radial measure for measuring the efficiency of decision making units with negative data, using DEA. European Journal of Operational Research, 200, 297-304. ] introduced a Semi-Oriented Radial Measure (SORM) for modeling DEA with negative data. The current paper presents a modification of the SORM model to accommodate such flexible measures, and indeed a model is proposed to evaluate the efficiency of decision making units (DMUs) where flexible and negative data exist. Several examples illustrate the proposed approach. Keywords: Data envelopment analysis, Negative data in DEA, Flexible measure, Efficiency