A census involves gathering information from every member of the population. A common use of census is by governments, when recording the country’s population statistics to inform policy and planning.
Because of the large size of most populations, and the resources required in conducting a census, this method is not commonly used unless absolutely necessary. Populations may be dispersed or inaccessible, making it impossible to achieve a complete census even if desired. Due to the time and labor involved in reaching the population, as well as entering the data and interpreting it, a census can be extremely expensive to conduct.
While a census provides the greatest accuracy of results as compared to other data collection methods, the increase in accuracy usually does not justify the added cost. An exception to this may be where the population size is very small.
The inclusion of minority, marginalized, and undocumented populations is also a challenge for censuses. These populations may be overlooked as a result of methodology, or by intent.