||Data envelopment analysis (DEA) is a linear programming-based technique for measuring the relative performance of organizational units where the presence of multiple inputs and outputs makes comparison difficult. DEA can be used in a number of ways to elaborate on the performance of individual units and to ascertain how the units can become more efficient. Some of the uses of which DEA can be put are the following: 1. using peer groups, 2. identifying efficient operating practices, 3. target setting, 4. identifying efficient strategies, 5. monitoring efficiency changes over time, and 6. resource allocation. The DEA models originally developed for comparative efficiency assessments have subsequently been modified to enable efficiency assessments to be carried out in certain special situations. DEA can be used to carry out comparative efficiency assessments in cases where returns to scale are not constant and in cases where certain inputs and/or outputs can only be measured on an ordinal scale.