A measure of viewing to commercial spots. One impact is one member of the target audience viewing one commercial. Impacts are added together to give, e.g. the total impacts delivered by a particular spot, the gross total achieved by a particular advertising campaign, or the total supplied by a given channel. A total of 10 impacts could be achieved in a number of ways: by ten people viewing a single commercial, or by one person seeing the commercial ten times, or by five people seeing the commercial twice etc.