A reliable census is important for a country to adequately plan growth, deliver services and solve the country's problems. For example, a national government distributing economic assistance to local governments can use census data to direct aid to parts of the country with the highest poverty rates.
A census can help a country with representative government decide how much power each individual state and local government has in determining the direction of the country. The United States uses its census to determine how many representatives each state can elect to represent its citizens in the House of Representatives in Congress. This number of representatives is determined every 10 years by the population of each state.