A modified super-efficiency DEA model for infeasibility

The super–efficiency data envelopment analysis (DEA) model is obtained when a decision making unit (DMU) under evaluation is excluded from the reference set. This model provides for a measure of stability of the ‘efficient’ status for frontier DMUs. Under the assumption of variable returns to scale (VRS), the super efficiency model can be infeasible for some efficient DMUs, specifically those at the extremities of the frontier. The current study develops an approach to overcome infeasibility issues. It is shown that when the model is feasible, our approach yields super–efficiency scores that are equivalent to those arising from the original model. For efficient DMUs that are infeasible under the super–efficiency model, our approach yields optimal solutions and scores that characterize the extent of super–efficiency in both inputs and outputs. The newly developed approach is illustrated with two real world data sets.