A statistic measuring the total number of unique people or households exposed to a medium over a specific period of time. Reach refers only to the number of people or households who are exposed to the medium, not to the number of people or households who actually experience the medium in question.
A given viewer is said to have been “reached” when they have viewed the medium during a specified period.
Reach is commonly stated as either an absolute number or as a fraction of a given population. For example: “men,” “women,” “children age 8 to 11.” Multiple or extended viewing(s) in the specified period does not increase reach. The term “effective reach” describes the quality or quantity of exposure.
Reach is a time dependent measurement and must be reported as such. For example: “TV channel X had a one-day reach of 2356 viewers per million on January 01, 2007.” Effective reach may be factored into the statistic by including a qualifier. For example: “On January 01, 2007 2536 views per million watched TV channel X for at least 10 minutes.
Reach was first clinically described by Hermann Ebbinghaus (January 24, 1850 — February 26, 1909) a German psychologist who instigated the experimental study of memory.