One key to The Avengers' record success this weekend: its PG-13 rating. The top six highest-grossing movies ever made are all rated PG-13; the rating points to a film that's titillating enough for teens but isn't likely to offend adults, the Los Angeles Times notes. The rating has become a Holy Grail for movie execs, particularly lately. Last year, R-rated movies accounted for 21% of US box office takings—the lowest figure in decades.
PG-13 movies, meanwhile, managed 54%—even though just 35% of films received the rating. This summer will see the release of a host of blockbusters rated PG-13, from The Dark Knight Rises to Battleship, as studios fight to receive the rating. Ratings organization the MPAA has heard nine ratings appeals this year, six of which were efforts to shift Rs to PG-13s. One problem with the R rating: It's an "incredibly broad category," making it tough for audiences to know what they're in for, says a Sony exec. (Read more Avengers stories.)