<P> A census is the procedure of systematically acquiring and recording information about the members of a given population . The term is used mostly in connection with national population and housing censuses; other common censuses include agriculture, business, and traffic censuses . The United Nations defines the essential features of population and housing censuses as "individual enumeration, universality within a defined territory, simultaneity and defined periodicity", and recommends that population censuses be taken at least every 10 years . United Nations recommendations also cover census topics to be collected, official definitions, classifications and other useful information to co-ordinate international practice . </P> <P> The word is of Latin origin: during the Roman Republic, the census was a list that kept track of all adult males fit for military service . The modern census is essential to international comparisons of any kind of statistics, and censuses collect data on many attributes of a population, not just how many people there are . Censuses typically began as the only method of collecting national demographic data, and are now part of a larger system of different surveys . Although population estimates remain an important function of a census, including exactly the geographic distribution of the population, statistics can be produced about combinations of attributes e.g. education by age and sex in different regions . Current administrative data systems allow for other approaches to enumeration with the same level of detail but raise concerns about privacy and the possibility of biasing estimates . </P>

When is a census of the population to be taken