A modification on 'ranking DMUs by L1-norm' and introducing a novel ranking method by Tchebycheff norm with fuzzy data in DEA

Jahanshahloo et al. (2009) proposed a ranking model to efficient decision‐making units (DMUs) including fuzzy data. The aforementioned method is based on L1-norm measure combined with the weighted signed distance between two fuzzy numbers. Firstly, it is shown by an example that the proposed method may not work correctly. And then, the modification of the method is presented in this paper. What is more, for more extension, another approach is introduced to ranking extremely efficient decision‐making units in data envelopment analysis (DEA) models with fuzzy data. This approach is based on the Tchebycheff norm (infinity norm). Then, it is shown that this new model can address some shortcoming of the L1-norm proposed by previous authors. Finally, to demonstrate the concept, the case of 30 branches of social welfare bureau in Tehran is revisited and solutions are compared.