Age
Ages relate to age at last birthday. Average ages (for example, average age at death or at childbirth) are calculated using age at last birthday, assuming that events occur halfway through each year of age (that is, adding 0.5 years). For example, when calculating the average age at death, it is assumed that the average age of 77‑year‑olds who died was 77 years and 6 months.
Rates
Rates relate the number of events to the size of the population at risk, enabling meaningful comparisons over time or between populations.
Crude rate
A crude rate is defined as the number of events (for example, births or deaths) occurring within a specified population over a defined period, typically expressed per 1,000 or 100,000 individuals per year.
A direct comparison of crude birth or death rates between areas may be misleading because of differences in the age and sex structure of the populations.
Age-specific rates
Age‑specific rates are calculated by dividing the number of events in a specific age group by the population of that age group. For births, the denominator is the female population only. Rates are typically expressed per 1,000 individuals.
Age-standardised rates
These rates adjust for differences in age structure, allowing trends over time to be compared on a consistent basis.
