This is the method used by TV stations to measure viewership and devise ratings for all the shows. This is done by Neilsen Media research. The company conducts research using three methods.
Local People Meters (LPMs)
In about 14, 000 homes which encompasses about 35,000 people in the USA, Neilsen installs special boxes with special remotes that transmit data to their research headquarters. These homes are usually located in the large markets (ie New York, Chicago, LA, Houston). Each member of the each house hold has a special button on the remote that is designated for their TV usage. This way, Neilsen will know who is watching what show at what time.
Similar to LPMs except they don’t monitor who is watching, just what is being watched. Again, this set meter is installed in about 10,000 homes through the USA.
Neilsen will pay certain households in smaller markets to fill out a diary of what shows they watched throughout each day and deliver it to Neilsen at the end of each week.