The X rating was an old rating that was used by the United States to signify adult material. It was replaced by the NC-17 rating. The reason for this was because after the rating system took effect, the pornography industry (whose films are not rated by the MPAA, because they have nothing to do with the Hollywood entertainment industry) started branding X as an advertising gimmick. Suddenly, people equated X with pornography. Most video stores refused to stock X-rated material. Some studios were even forcing directors to make cuts in their films in order to ensure an R rating. In time, word got out and NC-17 was created in 1990 by the MPAA. The NC-17 rating was copyrighted, ending the pornography craving for good.
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