A census counts every person in a country or area. UNFPA, the United Nations Population Fund, calls it one of the biggest and hardest jobs a nation takes on in peacetime.
What a census counts
A census gives the total number of people and shows where they live. It also records their age, their sex and how they live, according to UNFPA.
How often it happens
UNFPA says a census should take place once every 10 years. It calls each 10-year cycle a “round”. The current round runs from 2025 to 2034.
Why the numbers matter
Census data help governments plan. UNFPA says they are critical for good government, policy and planning for growth. They also help with welfare programmes, business research and responses to crises. UNFPA adds that in many countries, only the census shows who is being left out of society and the economy. It also says 107 of the 232 Sustainable Development Goals indicators need population data.
How the counting is done
UNFPA says counts are moving to new tools, such as handheld devices and mapping software. Some countries use school, health clinic and ID records to count people without visiting every home. UNFPA calls this a register-based census. Where records fall short, countries can add visits to homes.
How it works in the United States
The US Constitution requires a count of every resident every 10 years. The rule is in Article I, Section 2. The 2020 Census was the 24th count, and the first took place in 1790. Each home was invited to answer online, by phone or by mail. For the first time, everyone could answer online.
The US Census Bureau says the results decide how many House seats each state gets. They also help redraw voting districts. The Bureau adds that the results guide hundreds of billions of dollars of government money for schools, roads, hospitals and more. In 2020, the US had about 330 million people and over 140 million housing units to count.
When people are missed
Not every country counts everyone. UNFPA says 35 countries did not hold a census in the 2020 round. It estimates that about 2.4 billion people went uncounted. That is nearly 30 percent of the world.
