A census is the process of obtaining information about every member of a population (not necessarily a human population). It can be contrasted with sampling in which information is only obtained from a subset of a population. As such it is a method used for accumulating statistical data.
Rome conducted censuses to determine taxes. The word census derives from the Roman censor, the official in charge of counting Romans and setting tax rates. In the Bible, The Book of Numbers describes a God-mandated census that occurred when Moses led God's people from Egypt. King David of Israel commanded a numbering of the people which is strongly condemned. Although it is not entirely clear why, conservative and evangelical Biblical scholars believe that God did not intend the United Kingdom under Kings David and Solomon to rely on its own strength in warfare. Another reason given is that, as in the case of Roman and Egyptian censuses, the census would be used to determine taxation. A Roman census is also mentioned in the Book of Luke of New Testament of the Bible.
The Canadian census is run by Statistics Canada. The first census conducted in Canada was conducted in 1666, by French intendant Jean Talon, when he took a census to ascertain the number of people living in New France. In 1871, Canada's first formal census was conducted, which counted the population of Nova Scotia, Ontario, New Brunswick, and Quebec. In 1918, the Dominion Bureau of Statistics was formed. In 1971, Statistics Canada was formed to replace the Dominion Bureau of Statistics, and consequently, took over its census job.
Censuses in Canada are conducted in five year intervals. The latest census was conducted in 2001 and the next planned census is 2006. Censuses taken in mid-decade (e.g. 1976, 1986, 1996, etc.) are referred to as quinquennial censuses. Others are referred to as decennial censuses. The first quinquennial census was conducted in 1956.
Attempts at introducing a census in Germany sparked strong popular resentment in the 1980s since many quite personal questions were asked. Some campaigned for a boycott. In the end the Constitutional Court stopped the census in 1980 and 1983. The last census was in 1987. Germany has since used population samples in combination with statistical methods, in place of a full census.
The UK census as we know it today started in 1801, as part of a drive to ascertain the number of men able to fight in the Napoleonic wars. England took its first Census when the Domesday Book was compiled in 1086 for tax purposes. Dalriada (now Scotland) in the 7th century was the first territory in what is now the UK to conduct a census, with what was called the "Tradition of the Men of Alba" (Senchus fer n'Alba').
The census has been conducted every ten years since 1801 (except in 1941), the last one having been completed in 2001. The census is undertaken by the government, and the information is sold to interested parties, as well as being used for policy and planning purposes.
The 2001 census was the first year in which the government asked about religion. Perhaps encouraged by a chain letter that started in New Zealand, 390,000 people entered their religion as Jedi Knight (more than either Sikhs, Buddhists or Jews), with some areas registering up to 2.6% of people as Jedi.
The United States Constitution mandates that the census be taken at least once every ten years (Congress could require a more frequent census by legislation), and that the number of members of the House of Representatives from each state be determined accordingly. In addition, Census Bureau statistics are used for apportioning Federal funding for many social and economic programs.
The first U.S. Census was taken in 1790 by the local U.S. Marshals. In 1902, a Public Law established the Census Bureau as a permanent Federal agency. Until the 2010 census, there were two forms of questionnaire – long and short. Computer algorithms determine which form was mailed to a given household (in practice, of those households whose locations are on the Census Master Address List), one in six receiving the long form. This was supplemented by census workers who go door-to-door to talk to people who fail to return the forms. In addition to a simple count of residents, the Census Bureau collects a variety of statistics, on topics ranging from ethnicity to the presence of indoor plumbing.
Despite a massive effort, the Census Bureau has never been able to count every individual, leading to controversy about whether to use statistical methods to supplement the numbers for some purposes, as well as arguments over how to improve the actual head count. The Supreme Court has ruled that only an actual head count can be used to apportion Congressional seats; however, cities and minority representatives have complained that urban residents and minorities are undercounted. In several cases, the Census Bureau will recount an area with disputed figures, provided the local government pays for the time and effort. The State of Utah protested the figures of the 2000 decennial census because it lost a seat in the House of Representatives to North Carolina. Had the Census Bureau been able to count the numbers of Utahans living overseas, including many Mormon missionaries, Utah would have retained the seat.
To minimize the burden on individuals and to provide improved data, the Bureau is preparing several alternative methods for gathering economic, demographic, and social information, including the American Community Survey and record linking of depersonalized administrative records with other administrative records and Census Bureau surveys.
In additional to the decennial federal census, more localized versions are often used. An example of this is Massachusetts, which takes a statewide census every fifth year. Likewise, each community in Massachusetts takes a municipal census each year.