Analysing the difference due to risk and demographic factors for incidence or mortality

Background From an epidemiological and public health perspective there is an interest in quantifying differences in incidence and mortality between either time points, geographical areas or males and females. We propose a method for splitting such a difference in the number of cases/deaths into three components: (1) those due to risk; (2) those due to population structure (i.e. age distribution); and (3) those due to population size. We also propose graphical methods for presenting the results. Three examples are used to illustrate our methodology.