Question: I have a question that has been killing me for a long time. Every time
the Nielsen ratings come up, they always display ratings for a certain show by
age range. For instance, on a recent TV show, they said that it received the
most viewers between the ages of 18-24. How on earth do they know how old
the viewers are? How do they know if adults or teens watch their shows? While
we are on the subject, how do they calculate the viewer numbers? Is our
television some kinda tracking device? Basically, how do they know who is watching? — Johanna D.

Televisionary: Your TV isn’t a tracking device, Johanna, but the boxes the folks at Nielsen place in sample families’ homes certainly are. I’ve covered this before, but it’s been a while, so what the heck? Others are probably wondering about this kind of thing, too. Here are the basics.

Nielsen uses a representative sample of U.S. TV households to determine who’s
watching what and when — for obvious reasons, tracking each of the country’s
99 million households with TVs is out of the question. The sample is made up of
more than 5,000 houses, containing more than 13,000 viewers, that are randomly picked in order to represent a wide range of demographics and locales. Extrapolating from that, in theory, provides a picture of what the whole country is watching at any given time, within a certain range of error.

Exactly how do they measure? Using a few methods. They know the age, gender, etc. of each family member when they choose which households to work with. Meters are installed on every video device in the home — TV sets, cable boxes, VCRs, satellite dishes — to record which shows each is tuned to. Also, the company uses “people meters” to keep track of which person in the house is watching, and diaries and other methods are used to gather numbers on a market-by-market basis.