Census means the counting of the people. The word is a Latin one, and was applied to the functions which the Roman Censors (q.v.) performed of periodically enumerating the people, but no records of these enumerations remain, and indeed we have but a few scattered notices of them. In Greece a census was established by Solon at Athens for the double purpose of facilitating taxation and classifying the citizens. Religious prejudice prevented any censuses being taken during the middle ages, and it was not till the 18th century that the necessity for obtaining correct information as to the population of European countries overcame this feeling. The first country to undertake a census on a scientific basis was Sweden in 1749; in France an enumeration was made in 1700, but the first reliable was not taken till 1801. In America the first census was taken in 1790, and in England in 1801. Censuses are now taken in Austria, Belgium, Italy, Norway and Sweden, Russia, Switzerland, the United States of America, India, and most of the British colonies, every ten years; in France and Germany every five years; in Spain at irreg- ular intervals, the next after that of 1860 having been in 1877. The International Statistical Congress, which consists of eminent statisticians from all countries, has done much to improve the taking of censuses, and now several countries, such as Austria, Belgium, Italy, Prussia, Russia, and Switzerland, have statistical bureaux for the purpose, amongst other things, of controlling the taking of the periodical census. In a few countries information as to the religion of the population, and in some cases additional particulars, are obtained, such as the census of 'useful domestic animals' in Norway.
In the United Kingdom the practice is for parliament to pass special acts directing the taking of each census. These acts provide that the registrars of births and deaths shall be the officers through whom the census is to be taken by enumerators, of whom at the census of 1891 there were upwards of 40,000 employed in Great Britain. All the registrars' districts are so subdivided that no enumerator has more houses than he can conveniently visit in one day. The enumerators have to deliver schedules at all houses, requiring particulars concerning every person who is alive at midnight preceding the census day, and on the census day to collect them. Account has also to be taken of all persons not dwelling in houses wherever found, and of persons travelling, and persons in ships, barges, &c. The enumerators are authorised to require the information necessary for the census, and persons refusing to answer or wilfully giving false answers to the questions are rendered liable to penalties. The particulars to be required in each census are specified in the act directing it to be taken. The Census Act, 1900, required that the census of the following year should show 'the name, sex, age, rank, profession or occupation, condition as to marriage, relation to head of family, and birthplace of every living person who abode in every house on the night of Sunday the 31st of March 1901, and also whether any were blind or deaf and dumb, or imbecile or lunatic.' When the schedules have been collected they are transmitted to the census office, where the work of tabulation, which takes about two years, is carried out. The census when finished is presented to parliament in the form of several bulky volumes. Hardly any two countries agree as to the subjects on which information is demanded; thus some census schedules contain inquiries as to whether there are in the household infirm persons, blind, deaf and dumb, idiots, insane persons, persons who have been convicted of crime; how many languages are spoken by the persons entered; how many are at school; how many exercise the franchise; how many rooms and windows there are in the house, and so on. In 1851 an attempt was made to obtain religious statistics of the United Kingdom; since that year the census shows the religious statistics of Ireland only.
The census of the United States aims at giving a specially full conspectus of the condition of the people, and is illustrated by a large number of maps bearing on almost every branch of the census inquiries. Thus there are maps showing the prevalence of certain diseases; others the area occupied by various crops. The United States census of 1880 extends to 22 volumes. Its compilation took an exceedingly long time, the delay being mainly due to congress having failed to make the necessary appropriations of money for the purpose. The bill for the taking of the census of 1890 somewhat limited the scope of the inquiry as compared with the censuses of previous years.