malmquist productivity index in several time periods on interval data

the productivity change of a decision making unit (dmu) between two time periods can be evaluated by the malmquist productivity index. in this study, we propose a method to compute the malmquist productivity index in several time periods (from the first to the last periods) on interval data in data envelopment analysis (dea). then, the obtained malmquist productivity index is compared with malmquist productivity index between two time periods (the first and last time periods) on interval data. the aim of this paper is to investigate the progress and regress of decision making units (dmus) in several time periods by considering all time periods between the first and the last one, on interval data. consequently when the malmquist productivity index is computed in several time periods, progress and regress of decision making units can be evaluated more carefully than before. what is more, one can judge with greater accuracy whether or not such strategy are favorable and promising. lastly, a numerical demonstration illustrates the procedure of the proposed method then some conclusions are reached, and directions for future research are suggested.