zgi is a recentered influence function on the quantile of interest of the distribution of disposable equivalised income the group differences in the predictors are weighted by the coefficients of families characteristics in to determine the endowments effect the so called explained component in other words this latter measures the expected change in income quantiles if those families had mid s predictor levels by contrast the second term estimates the portion of the evolution of income that is due to changes in the association between poverty and household characteristics applied to predictor levels and it measures the income difference resulting from variations in the returns that family and work characteristics from one period to the other differences which are mainly due to changes in the distribution of market income and in the structure of social transfers