Records of births, deaths, marriages, immigration and emigration and a regular census of population provide information that is key to making sound decisions about national policy.
It provides data about the sex and age distribution of the population in an accessible graphical format.
For a cohort of persons born in the same year, it traces and projects their life experiences from birth to death.
For a given cohort, the proportion expected to survive each year (or decade in an abridged life table) is presented in tabular or graphical form.
Also, some people counted in the census may be recorded in a different place than where they usually live, because they are travelling, for example (this may result in overcounting).
Between censuses, administrative data collected by various agencies about population events such as births, deaths, and cross-border migration may be used to produce intercensal estimates.