How do TV networks know when viewers are watching a specific show?
—Ruth F., Missouri
A New York-based company called Nielsen Media Research is responsible for television ratings. "We rely on sampling and we recruit homes across the country to be a part of Nielsen's sample. It is a random selection process; we don't take volunteers. We choose a sample of homes that represent the U.S. as closely as possible," says Karen Gyimesi, Nielsen's vice president of communications. The sample covers a variety of demographics, household sizes, ethnicities and ages, and it polls each home for a maximum of two years. The most publicized sample is the national people meter, where a box is installed in every room and each person is assigned a button. They must log into the people meter when they watch television. "We are always looking at how the demographics of the U.S. are changing so we can make sure our sample is mirroring that as accurately as possible," Gyimesi says. Instead of keeping a meter, some viewers are asked to keep a paper diary for one week, which is used as a supplement to create a ratings book for local TV markets around the country.