With the widespread arrival of sound film in American theaters in 1929, many independent exhibitors began dropping the then-dominant presentation model, which involved live acts and a broad variety of shorts before a single featured film. A new programming scheme developed that would soon become standard practice: a newsreel, a short and/or a serial, and a cartoon, followed by a double feature. The second feature, which actually screened before the main event, cost the exhibitor less per minute than the equivalent running time in shorts. The majors' comprehensive booking policy, which would become known as the "run-zone-clearance" system, inadvertently pushed independent theaters toward adopting the double-feature format. As described by historian Thomas Schatz, the system "sent a picture, after playing in the lucrative first-run arena, through the 16,000 'subsequent-run' movie houses; 'clearance' refers to the amount of time between runs, and 'zone' refers to the specific areas in which a film played.