Another study has called into question the effectiveness of America's movie rating system. Researchers at the Dartmouth Medical School have found that a large number of children under 15 (nearly 13% of the estimated 22 million youth in the U.S.) are exposed to graphic depictions of violence in films. The study uses data from a national 2003 telephone survey of kids ages 10 to 14 and looks at exposure to the 40 most violent films. More details of the study are available at the Dartmouth Medical School web site.