malmquist productivity index in several time periods

the malmquist productivity index evaluates the productivity change of a decision making unit (dmu) between two time periods. in this current study, a method is proposed to compute the malmquist productivity index in several time periods (from the first to the last periods) in data envelopment analysis (dea) and then, the obtained malmquist productivity index is compared with malmquist productivity index between two time periods (the first and the last time periods). the aim of this paper is to investigate progress and regress of decision making units (dmus) in several time periods considering all time periods between the first and the last one. consequently, when malmquist productivity index is computed in several time periods, progress and regress of decision making units can be evaluated more carefully than before. at last, a numerical demonstration reveals the procedure of the proposed method then some conclusions are reached and directions for future research are suggested.