United States Census Bureau
The Constitution of the United States says that the population must be counted at least once every ten years (through the U.S. Census). This is done to calculate how many Federal Representatives in Congress each state should have. The Census Bureau is in charge of doing this. It collects statistics about the nation, its people, and its economy. The Census Bureau's legal authority is listed in Title 13 of the United States Code. The first census bureau was in 1790.