Census
A census is the procedure of systematically acquiring, recording, and calculating information about the members of a given population, which are then usually displayed through statistics. This term is used mostly in connection with national population and housing censuses; other common censuses include censuses of agriculture, traditional culture, business, supplies, 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 ten years. UN recommendations also cover census topics to be collected, official definitions, classifications, and other useful information to coordinate international practices.
The UN's Food and Agriculture Organization, in turn, defines the census of agriculture as "a statistical operation for collecting, processing and disseminating data on the structure of agriculture, covering the whole or a significant part of a country." "In a census of agriculture, data are collected at the holding level."
The word is of Latin origin: during the Roman Republic, the census was a list of all adult males fit for military service. The modern census is essential to international comparisons of any type of statistics, and censuses collect data on many attributes of a population, not just the number of individuals. 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 and citizenship estimates remain an important function of a census, including exactly the geographic distribution of the population or the agricultural 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.
A census can be contrasted with sampling in which information is obtained only from a subset of a population; typically, main population estimates are updated by such intercensal estimates. Modern census data are commonly used for research, business marketing, and planning, and as a baseline for designing sample surveys by providing a sampling frame such as an address register. Census counts are necessary to adjust samples to be representative of a population by weighting them as is common in opinion polling. Similarly, stratification requires knowledge of the relative sizes of different population strata, which can be derived from census enumerations. In some countries, the census provides the official counts used to apportion the number of elected representatives to regions. In many cases, a carefully chosen random sample can provide more accurate information than attempts to get a population census.
History
Iran
One of the earliest systematic censuses in world history was conducted during the early Achaemenid period, up until the reign of Darius The Great in Ancient Iran. This census, aimed at financial planning, military organization, and tax collection, spanned regions across three continents: Asia, Africa, and Europe. It included data on population numbers, the wealth of cities and provinces, precise assessments of agricultural lands, the resources of each region, and other factors critical to determining state finances and planning for governance and military operations.Egypt
The earliest Egyptian census was the cattle count, which counted not people but livestock for taxation purposes. During the early Old Kingdom it was taken every two years; the frequency increased over time. Human censuses in Egypt first appeared in the late Middle Kingdom and developed in the New Kingdom. Herodotus wrote that Ahmose I, first monarch of the New Kingdom, required every Egyptian to declare annually to the nomarch, "whence he gained his living". Under the Ptolemies and the Romans several censuses were conducted in Egypt by government officials.Ancient Greece
There are several accounts of ancient Greek city states carrying out censuses.Israel
Censuses are mentioned several times in the Biblical narrative. God commands a per capita tax to be paid with the census for the upkeep of the Tabernacle. The Book of Numbers is named after the counting of the Israelite population according to the house of the Fathers after the exodus from Egypt. A second census was taken while the Israelites were camped in the "plains of Moab". King David performed a census that produced disastrous results. His son, King Solomon, had all of the foreigners in Israel counted.China
One of the world's earliest preserved censuses was held in China in AD2 during the Han dynasty, and is still considered by scholars to be quite accurate. The population was registered as having 57,671,400 individuals in 12,366,470 households but on this occasion only taxable families had been taken into account, indicating the income and the number of soldiers who could be mobilized. Another census was held in AD144.India
The oldest recorded census in India is thought to have occurred around 330BC during the reign of Emperor Chandragupta Maurya under the leadership of Chanakya and Ashoka.Rome
The English term is taken directly from the Latin census, from . The census played a crucial role in the administration of the Roman government, as it was used to determine the class a citizen belonged to for both military and tax purposes. Beginning in the middle republic, it was usually carried out every five years. It provided a register of citizens and their property from which their duties and privileges could be listed. It is said to have been instituted by the Roman king Servius Tullius in the at which time the number of arms-bearing citizens was supposedly counted at around 80,000.In AD6, the Roman legate Publius Sulpicius Quirinius organized a census of Judaea for tax purposes, which was partially responsible for the development of the Zealot movement and several failed rebellions against Rome ultimately ending in the Jewish Diaspora. The Gospel of Luke makes reference to Quirinius' census in relation to the birth of Jesus; based on variant readings of this passage, a minority of biblical scholars, including N. T. Wright, speculate that this passage refers to a separate registration conducted during the reign of Herod the Great, several years before Quirinius' census.
The 15-year indiction cycle established by Diocletian in AD297 was based on wikt:quindecennial censuses and formed the basis for dating in late antiquity and under the Byzantine Empire.
Rashidun and Umayyad Caliphates
In the Middle Ages, the Caliphate began conducting regular censuses soon after its formation, beginning with the one ordered by the second Rashidun caliph, Umar.Medieval Europe
The Domesday Book was undertaken in AD1086 by William I of England so that he could properly tax the land he had recently conquered. In 1183, a census was taken of the crusader Kingdom of Jerusalem, to ascertain the number of men and amount of money that could possibly be raised against an invasion by Saladin, sultan of Egypt and Syria.The first national census of France was undertaken in 1328, mostly for fiscal purposes. It estimated the French population at 16 to 17 million.
Inca Empire
In the 15th century, the Inca Empire had a unique way to record census information. The Incas did not have any written language but recorded information collected during censuses and other numeric information as well as non-numeric data on quipus, strings from llama or alpaca hair or cotton cords with numeric and other values encoded by knots in a base-10 positional system.Spanish Empire
On May 25, 1577, King Philip II of Spain ordered by royal cédula the preparation of a general description of Spain's holdings in the Indies. Instructions and a questionnaire, issued in 1577 by the Office of the Cronista Mayor, were distributed to local officials in the Viceroyalties of New Spain and Peru to direct the gathering of information. The questionnaire, composed of fifty items, was designed to elicit basic information about the nature of the land and the life of its peoples. The replies, known as "relaciones geográficas", were written between 1579 and 1585 and were returned to the Cronista Mayor in Spain by the Council of the Indies.Sampling
A census is often construed as the opposite of a sample as it intends to count everyone in a population, rather than a fraction. However, population censuses do rely on a sampling frame to count the population. This is the only way to be sure that everyone has been included, as otherwise those not responding would not be followed up on and individuals could be missed. The fundamental premise of a census is that the population is not known, and a new estimate is to be made by the analysis of primary data. The use of a sampling frame is counterintuitive as it suggests that the population size is already known. However, a census is also used to collect attribute data on the individuals in the nation, not only to assess population size. This process of sampling marks the difference between a historical census, which was a house-to-house process or the product of an imperial decree, and the modern statistical project.The sampling frame used by a census is almost always an address register. Thus, it is not known if there are any residents or how many people there are in each household. Depending on the mode of enumeration, a form is sent to the householder, an enumerator calls, or administrative records for the dwelling are accessed. As a preliminary to the dispatch of forms, census workers will check for any address problems on the ground. While it may seem straightforward to use the postal service file for this purpose, this can be out of date and some dwellings may contain several independent households. A particular problem is what is termed "communal establishments", a category that includes student residences, religious orders, homes for the elderly, people in prisons, etc. As these are not easily enumerated by a single householder, they are often treated differently and visited by special teams of census workers to ensure they are classified appropriately.