Correction: In preparing this material, an arithmetic error led to a substantial underestimate of PG-13 tobacco impressions May-October 2006 and the conclusion that PG-13 tobacco impressions had tripled in May-October 2007, compared to the same period the year before. 2007 PG-13 impressions for these months, which were correctly reported, actually were slightly lower than in 2006. We regret the error. A correction was published in the 48th Smoke Free Movies ad.