Egypt's first census counted cows, not people
Long before governments tallied citizens, ancient Egyptian officials were counting cattle. The earliest Egyptian census recorded livestock for taxation, held every two years in the early Old Kingdom. People only became the subject of regular counts much later, and the idea has shaped how states tax, recruit and govern ever since.
The word comes from the Latin censere, to assess. In the Roman Republic the census listed every adult male fit for military service. The United Nations now describes a proper population census by four features: counting individuals, covering a whole defined territory, happening at one time, and repeating at regular intervals, ideally at least once a decade.
Ancient empires relied on counts for money and armies. The early Achaemenid Persian state, up to the reign of Darius the Great, surveyed population, the wealth of provinces and farmland across territory spanning three continents. In Egypt, human censuses appeared in the late Middle Kingdom, and Herodotus reported that Ahmose I required every Egyptian to declare each year how he earned his living. The Han dynasty's census of AD 2, one of the oldest preserved, recorded 57,671,400 people in 12,366,470 households, counting only taxable families, and scholars still regard it as fairly accurate. The Bible's Book of Numbers takes its name from a count of the Israelites after the exodus.
Modern censuses gather far more than headcounts, allowing statistics such as education by age and sex across regions. They supply the frame for designing surveys, such as address registers, and the figures pollsters use to weight samples so they represent the whole population. In some countries they decide how many elected representatives each region receives, which can spark legal disputes.
A census is not always the most precise tool. A carefully drawn random sample can sometimes yield more accurate results than an attempt to count everyone, and between censuses, sample-based estimates keep figures current. Administrative records now offer another route to similar detail, though they raise concerns about privacy and possible bias.
Source: Census
