Abstract: Scale efficiency analysis is an important problem in traditional DEA research.However,the existing literatures have not studied the influencing factors and degrees to scale efficiency.This paperuses the weight-variable DEA model in which the input weight is defined by a piecewise linear function,discovers that the factor discount is one source of scale efficiency,and measures the contribution of factor discount to scale efficiency.Anumerical example is given to illustrate that there are differences on the contri-bution of factor discount to scale efficiency for different enterprises and different discountratios.For some enterprises the scale efficiency increases with increasing discountratio,but for some else the scale efficiency decreases.

Key words: data envelopment analysis, scale efficiency, diverse weight, efficiency evaluation