The total number of events (e.g. cases of lung cancer) expressed as a percentage (or rate per 1000, etc.) of the whole population. When factors such as age structure or sex of populations may seriously affect their rates (as in mortality or morbidity rates) it is more meaningful to compare age/sex specific rates using one of more age groups of a designated sex (e.g. lung cancer in males aged S5-64 years) More complex calculations, which take account of the age bias of a population as: whole, can produce standardized rates of standardized mortality ratios (SMR). In these the ratios of subgroups are expressed as percentages of that for a designated of standard population.