Y.-M. Wang, Y.-X. Lan / Mathematical and Computer Modelling 54 (2011) 2760–2771 2761 TheDEA-basedMPI has proven to be a very useful tool formeasuring the productivity changes of DMUs in the past several decades. For instance, Färe et al. [13] applied it to analyze the productivity growth in industrialized countries. Grifell-Tatjé and Lovell [14] used it tomeasure the effect of deregulation on S...