The U.S. Census counts every resident in the United States, and is required by the Constitution to take place every 10 years.
"The actual enumeration shall be made within three years after the first meeting of the Congress of the United States, and within every subsequent term of 10 years, in such manner as they shall by Law direct."
-- Article I, Section 2 of the Constitution of the United States
Census information affects the numbers of seats your state occupies in the U.S. House of Representatives. And people from many walks of life use census data to advocate for causes, rescue disaster victims, prevent diseases, research markets, locate pools of skilled workers and more.
"...an accurate count of the U.S. population forms the basis for many important but often overlooked political, economic, and social decisions that are made that end up affecting our daily lives."
-- C.N. Le, Professor at University of Massachusetts, Amherst
The information the census collects helps to determine how more than $400 billion dollars of federal funding each year is spent on infrastructure and services including: