Editing Demographic statistics (section)

==Collection==
National population statistics are usually collected by conducting a [[census]]. However, because these are usually huge logistical exercises, countries normally conduct censuses only once every five to 10 years. Even when a census is conducted it may miss counting everyone (known as [[undercount]]). 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 [[overcount]]ing). Consequently, raw census numbers are often adjusted to produce ''census estimates'' that identify such statistics as ''resident population'', ''residents, tourists and other visitors'', ''nationals and aliens (non-nationals)''. For privacy reasons, particularly when there are small counts, some census results may be rounded, often to the nearest ten, hundred, thousand and sometimes randomly up, down or to another small number such as within 3 of the actual count.

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 estimate]]s.