Bessent et al (1988) coined this term (later simply known as unenveloped units) to refer to those inefficient units that are not fully enveloped by the efficiency frontier. To be fully enveloped in the CCR model, an inefficient DMU needs to have (m+n) -1 reference units where m+n denotes the number of factors. Unenveloped units can be identified from the results of the ratio models as those units with non-zero values in any of their input or output slacks. [Bessent A, Bessent W, Clark T and Elam J (1988) ‘Efficiency frontier determination by constrained facet analysis’, Operations Research, 36, pp 785-706.]
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FAQ
- What is Data Envelopment Analysis?
- BCC
- Categorical variable
- CCR (ratio) mode
- Composite unit
- Constant returns to scale
- Convex cone - Conical hull
- Convex hull
- Convexity constraint
- Cross efficiency matrix
- DEA algorithm
- DEA results are biased
- Decreasing returns to scale
- Discretionary factor
- Discriminatory power
- DMU (Decision making unit)
- Dual Model
- Dual weights - dual multipliers
- Efficiency score
- Efficiency/Productive efficiency
- Envelopment form
- Environmental factor
- Epsilon
- Exogeneously fixed factor
- Facet
- Homogeneity
- Increasing returns to scale
- Input
- Input-oriented
- Input/output mix
- Isotonicity
- Most productive scale size (MPSS)
- Multiplier form
- Non-naturally enveloped unit
- Nondiscretionary factor
- Ordinal variable
- Outlier
- Output
- Output-oriented
- Overall efficiency
- Pareto-efficiency/Pareto-Koopmans efficiency:
- Peer group
- Piecewise linearity
- Primal (CCR) model
- Production function
- Productivity
- Projected point
- Radial measure
- Ratio models
- Reference set
- Reference unit
- Scale efficiency
- Scale of operations
- Slacks
- Targets
- Technical efficiency
- Technology/Production technology
- Unit
- Unit isoquant/Isoquant
- Units invariance
- Variable
- Variable returns to scale
- Virtual input(output)
- Virtual multipliers
- Visualisation
- Weight Flexibility
- Weights
- Well-rounded performance
- Window analysis