This paper introduces coefficient of variation(  CV  2  ) of incidence risk which is influenced by epidemiologic risk factor(s) to evaluate individual and collective impact of risk factors on the incidence of population under investigation.The estimation of   CV    2 for single risk factor and multiple risk factor by means of the stratification and Logistic discriminant score is applied to data on cancer of the esophagus.The   CV    2 values for impact of drinking alcohol on incidence of cancer of the esophagus in different age groups are estimated, and compared with the attributable fractions.It is believed from the method and results that coefficient of variation has advantage of not depending on an arbitrary classification of a baseline category and can be used as a measure of risk attribution and complement measure for the relative risk and attributable fraction.