If you live in the U.S., every ten years you'll participate in a census, a process for counting people. The information collected is used to plan for schools, transportation, social services people will need, and also for determining congressional districts.
On the census form you’ll be asked how many people live in your house, their ages, and ethnic and racial backgrounds. With this, the government can plan facilities and also track population trends — whether cities are growing or shrinking, what ethnic groups make up our population, and where they live. We get the word and the idea from the Romans, who registered citizens and their property so they could be taxed. The first U.S. census was held in 1790.