Electronic metering technology is the heart of the Nielsen ratings process. We use two types of meters: set meters capture what channel is being tuned, while People Meters go a step further and gather information about who is watching in addition to the channel tuned.
Diaries are also used to collect viewing information from sample homes in many television markets in the United States, and smaller markets are measured by paper diaries only. Each year we process approximately 2 million paper diaries from households across the country for the months of November, February, May and July — also known as the “sweeps” rating periods. Seven-day diaries (or eight-day diaries in homes with DVRs) are mailed to homes to keep a tally of what is watched on each television set and by whom. Over the course of a sweeps period, diaries are mailed to a new panel of homes each week. At the end of the month, all of the viewing data from the individual weeks is aggregated.
This local viewing information provides a basis for program scheduling and advertising decisions for local television stations, cable systems, and advertisers.
In some of the mid-size markets, diaries provide viewer information for up to three additional “sweeps” months (October, January and March).
People Meter samples
Our national sample, composed of a cross-section of representative homes throughout the United States, is measured by a combination of set meters and People Meters. These meters give us information about not only what is being viewed on the set, but also exactly which members of the household are watching.
The People Meter is a “box” - about the size of a paperback book - that is hooked to each television and is accompanied by a remote control. Each family member in a sample household is assigned a personal viewing button, which is matched to that persons age and sex. Whenever the TV is turned on, a light flashes on the meter, reminding viewers to press their assigned button and indicate that they are watching television. Additional buttons on the People Meter enable guests who are also watching to participate in the sample by entering their age, sex and viewing status into the system.
In addition to our national measurement, Nielsen currently measures the top 21 local markets using Local People Meter Technology, with plans for a total of 25 markets by 2010.
Set Meter samples
Large to mid-sized local markets below the top 21 (such as Milwaukee, San Antonio and Memphis) are measured by a different type of meter - one that gives information about set-tuning only. In these markets, demographic information is provided by a separate sample of people who fill out seven-day paper diaries (or eight-day diaries in homes with DVRs).