3. An Alternative Dynamic Slack-Based Model
Radial and non-radial are two types of efficiency measurements. The CCR and BCC models present radial
efficiency measurements. The slack-based measure of efficiency (SBM) is a non-radial measure of efficiency. The
non-radial approach SBM deals with slack directly, but neglects the radial characteristics of inputs and/or outputs.
Thus, the SBM measure reflects not only the weak efficiency values in CCR-efficiency but also the other (slack)
inefficiencies (Cooper et al., 2007). The SBM deals directly with the input excesses and output shortfalls of the
DMUs. However, the SBM measures the effectiveness of DMUs during a single period. It can be misleading to
decide on the DMUs’ performance during a single period. An optimization model should include the time change
effect. For these cases, dynamic DEA models have been developed. In this study, based on Tone’s (2001) SBM
and Lotfi and Poursakhi’s (2012) dynamic DEA model, we develop an alternative dynamic slack-based model
(DSBM).