Census findings serve as the basis for nearly $20 billion in federal money that Illinois gets every year for a vast array of needs — from highways and housing to health care and foster care. This state appears sure to lose one of its 18 seats in the U.S. House but could lose two. As that number shrinks, so does Illinois’ voice in the Electoral College. What’s the basis for the boundaries of federal, state and local voting districts? The census. And businesses from Walgreens to Walmart, sensitive to population growth or decline, use census data to help decide where to open and close stores.