From clay tablets to the Domesday Book: why were people counted in ancient times?

Today the word statistics brings computers and charts to mind. But its roots lie in a simple question: "How many people do we have?" Rulers were asking this question thousands of years ago.

• Mesopotamia. The UK Office for National Statistics (ONS) traces the tradition of the census back to a time even earlier than Rome and China, to Babylon, and says the records were made on clay tablets. The sources do not agree on the exact date of such records, so we do not give a date here. What matters is the idea: keeping a record of people and stocks is as old as writing itself.
• Rome and the word "census". The census, whose name comes from the Latin "censere" ("to assess"), recorded citizens and their property in Rome, and this determined their military and tax obligations. The ONS writes that this practice was started in the 6th century BC by the Roman king Servius Tullius. The register was kept by a special official, the censor.
• China, the Han dynasty. The data of the census of AD 2 is one of the oldest surviving population counts. According to the ONS, it recorded about 57.67 million people and 12.36 million households and is considered relatively accurate. Some sources, such as Britannica, give slightly different figures.
• England, the Domesday Book. According to the National Archives, William I (the Conqueror) ordered a survey of the whole kingdom at Christmas 1085, and it was completed in 1086. The aim was to know who each piece of land belonged to, who lived on it and how much it was worth.
• The common purpose. All these registers were drawn up for the needs of the state: food, taxes, soldiers and land. It is no coincidence that the word "statistics" itself is linked to the word "state" (status).
• The limits of the ancient method. People hid to avoid taxes, and counts dragged on for years. So the result was not an "exact figure" in today's sense but an approximate picture.

Example (prepared by the author, hypothetical figures). The governor of the ancient fortress "Ko'hna qal'a" asks the storekeeper: "Will the grain last through the winter?" According to the register there are 3 200 people, and each needs 15 kg of grain a month. Winter lasts 4 months: 3 200 × 15 × 4 = 192 000 kg. The granary holds 170 000 kg, so 22 000 kg are missing. Without the register, they would have found out about this shortage in the middle of winter. This is the first task of statistics: to reveal a problem in advance.