Historical background    The need of population counts came out in ancient times. It was associated with political, economic and military needs of ancient states that wanted information on the number of people that can pay taxes or be conscripted into the army.     Since the earliest states originated in ancient Egypt, China, in the basins of the Tigris and Euphrates rivers (Mesopotamia, Babylon, Assyria) in India, Japan, just in these ancient states conducted the first in human history population censuses, particularly, in Egypt (about 2800-2250 BC), China (in 2238 BC).     The first population censuses were of a primitive kind. Sometimes they were not recorded but bore a symbolic character. The Scythian king Arianta (Scythia was situated on a large part of the territory of modern-day Ukraine), wishing to get to know the number of his country commanded each Scythian, on pain of death for failing to do so, to bring an arrowhead.     Beginning from 435 BC, population censuses were conducted regularly in ancient Rome and throughout the Roman Empire. Censuses were carried out at birth place. In the Gospel one reads: “In those days a decree went out from Emperor Augustus that all the world should be registered. This was the first registration and was taken while Quirinius was governor of Syria. All went to their own towns to be registered. Joseph also went from the town of Nazareth in Galilee to Judea, to the city of David called Bethlehem, because he was descended from the house and family of David. He went to be registered with Mary, to whom he was engaged and who was expecting a child.” (New Testament, the Gospel of Luke, Ch.2)     During the Middle Ages (the V-th century – the middle of the XVII-th century) small and scattered states did not conducted systematic population censuses at the national level. Only because of exceptional circumstances - epidemics, famine, wars - upon their completion attempts have been made to count how many people remained alive. Only after the obviation of feudal lords and the formation of centralized states in the Middle Ages and their further strengthening in the XVIII century population censuses began to be conducted. However they have not taken into consideration all social classes, but only taxpayers and those subjected for recruiting, i.e. they have not been general, even when covered an entire state.     From the middle of XVIII century such counts were conducted in Austria, Bavaria, Holland, Denmark, Spain, and Japan.     In the created by the tsar Ivan the Terrible (Ivan Grozny) centralized state – the Tsardom of Muscov a tax assessment was performed by using conventional cadastral counts. In the XVII century a taxation unit becomes “a peasant homestead” (a household). In 1718 the tsar Peter I the Great introduced poll taxes (in contrast to chimney-money), in which only men population subject to taxes and recruiting was counted. Nobility, government officials, as well as some other officials were exempt from the counts. The first poll-tax lists drawn up in 1720-1721 were called “skazki”, the next counts were called revisions, and the lists – “the revision lists” (revizskiye skazki).     With the development of the capitalist mode of production all the regions of the country are combined into a unified national economic complex, in which deprived of production means, but personally independent from a capitalist workers (men, women and even children) are forced to find work and are free to migrate across the whole country and even beyond. In such circumstances the counts of just certain population categories inherent to feudal and slavery regimes (taxpayers, men for recruitment, etc.) become meaningless. Therefore, the need for general population censuses emerges, as a rule within the boundaries of a whole state.     Hence, the emergence and further development of general censuses called forth by the need to have detailed and regular information on the size, location and composition of the population are important for any period.     The first in the world practice general population census was the census of 1790 in the United States. In 1800 the first general censuses were carried out in Sweden and Finland, in 1801 - Britain, Denmark, Norway, France.     The programs of the first general censuses were very limited. Thus, by the first population census in the USA only the name of household’s head, the number of free persons, the number of white women and the number of slaves were registered; the first census in France - only gender and marital status of the population. There were no well-established procedures (instructions) to conduct censuses and their execution timing was very long. The first USA census took 18 months.     At the first stage of historical development of population censuses (the end of the XVIII-th century - the first part of the XIХ-th century) one dealt with laying the foundations of their organization and working out of programs. At the same time it was being realized the necessity to compare census data for different countries and harmonization of common recommendations.    Solving these problems has been dealt with at the second historic stage of the development of population censuses (the second half of the XIX-th century – the first part of the XX century). A decisive step towards their solution has made a prominent Belgian – Adolphe Quetelet (1796-1874). Formulated by him principles of the general population censuses were discussed at the first session of International Statistical Congress in 1853, which began convene on his initiative, then at the fourth - in 1860 and consolidated at the eighth session in 1872. In such a way the transition to population censuses in their modern sense was accomplished. Recommended programs of population censuses and their organization order do not remain constant, depending on time requirements they continue to improve, though the basic principles of their conduct are not out of date up for today.     By involving an ever greater number of countries in the international labour division system the need for conducting the World Census emerged, which is the aggregate of population censuses of individual states and territories of the world that are held at approximately the same time according to a unified principle. Approved in 1897 in St. Petersburg session of the International Statistical Institute a proposal to hold the World Census in 1900 was not implemented, as well as a proposal for the World Census 1940.     Conducting the World Census is made possible with the creation of the United Nations and its statistical apparatus with the formation of which starts the third historical stage of the development of population censuses.     The UN Statistical Commission in cooperation with the Commission on Population with an active participation of regional statistical conferences developed programs for the first World Censuses in 1950 and 1960. And further till the beginning of each decade a special document containing principles and recommendations regarding population and housing censuses, as well as tables templates for the development of census materials is produced. For today more and more countries adhere to these recommendations. Most of them conduct censuses once per decennium in years ending in “0”, “1” or “9”.    The resolution E/2015/10, adopted by the UN Economic and Social Council announced the next round of population and housing censuses in 2020 (from 2015 to 2024).