Perhaps providing at least a partial explanation for the poor performance of most R-rated films this year, the Federal Trade Commission said on Monday that ratings enforcement at the movie box office is at its highest level since the FTC began its mystery shopper program in 2000. The mystery shoppers were 13-16-year-olds who visited 250 theaters attempting to buy tickets to R-rated movies. Fewer than 25 percent of the underage moviegoers were able to do so, the FTC said, down from 33 percent in 2010. In a separate sting operation, the teens were sent to stores to buy R-rated videos and music CDs with Parental Advisory labels and M-rated videogames. Thirty percent of the shoppers were able to buy R-rated DVDs versus 38 percent in 2010. In a statement, John Fithian, president of the National Association of Theater Owners said, This report and its results continue to reinforce the importance and effectiveness of the voluntary ratings system. ... We will continue to do our part in enforcing the voluntary ratings system that allows creators to create and parents to make informed decisions about their children's entertainment.