Population statistics

Population statistics is the use of statistics to analyze characteristics or changes to a population. It is related to social demography and demography.

Population statistics can analyze anything from global demographic changes to local small scale changes. For example, an analysis of global change shows that population growth has slowed, infant mortality rates have declined and there have been small increases in the aged.

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 overcounting). 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 estimates.

Population estimates are usually derived from census and other administrative data. Population estimates are normally produced after the date the estimate is for.

Some estimates, such as the Usually resident population estimate who usually lives in a locality as at the census date, even though the census did not count them within that locality. Census questions usually include a questions about where a person usually lives, whether they are a resident or visitor, or also live somewhere else, to allow these estimates to be made.

Other estimates are concerned with estimating population on a particular date that is different from the census date, for example the middle or end of a calendar or financial year. These estimates often use birth and death records and migration data to adjust census counts for the changes that have happened since the census.

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