Nielsen ratings are audience measurement systems developed by Nielsen Media Research, in an effort to determine the audience size and composition of television programming in the United States. Nielsen Media Research was founded by Arthur Nielsen, who was a market analyst whose career had begun in the 1920s with brand advertising analysis and expanded into radio market analysis during the 1930s, culminating in Nielsen ratings of radio programming, which was meant to provide statistics as to the markets of radio shows. In 1950, Nielsen moved to television, developing a ratings system using the methods he and his company had developed for radio. That method has since become the primary source of audience measurement information in the television industry around the world. Electronic metering technology is the heart of the Nielsen ratings process. Two types of meters are used: 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 Nielsen processes 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.
53 mths ago