In what they are calling the largest-ever study linking tobacco use to television, researchers on Thursday said that a decline in the depiction of characters smoking in TV shows has led to a significant drop in the sales of cigarettes.

Researchers analyzed 1,838 hours of primetime dramas on broadcast TV — cable was excluded — that aired from 1955-2010 and determined that, at its peak in 1961 there were 4.96 instances of tobacco use per hour of programming. In 2010, that had dropped to just 0.29 instances per hour.

The researchers at the Annenberg Public Policy Center at the University of Pennsylvania, after adjusting for the rising cost of cigarettes, concluded that each instance of tobacco use was associated with 38.5 fewer cigarettes sold per person, per year in the U.S.