
The method of rating movies and the ratings themselves have been under close scrutiny, especially in the last few years. I believe that this scrutiny has come because in the last 40 years, since its creation, the method has only undergone minor changes, not really taking into account the world that has been changing around it.
On November 1, 1968, the Motion Picture Association of America (MPAA) introduced a new way to structure the classification of movies in American society. It was going to be a voluntary ratings system, in which filmmakers would submit their films for rating by a review board, and if they liked the rating that the movie got, it would continue on in its journey to the theaters. But if the producer did not like the rating that the film got, it would go back to the editors and they would cut and edit whatever needed to be taken out or changed so that it would achieve the rating that they originally planned for. This is how it is still done today. (As a side note, many of the editors and producers, when they go back to the editing room, figure out the bare minimum that would allow the movie to receive their desired rating, and that's what they take out. They have their agendas and they're going to do what's best for them)
Even before this voluntary system, though, the Hays Production Code was being used, a code that regulated what could and could not be showed on the new moving pictures, which were first showed in 1927. Up through the 1960's this code was used, although it had been continually revised to be more and more rigid as filmmakers produced movies with higher levels of promiscuity. For a good amount of time the code did its job, regulating and limiting the content of movies. But eventually producers found ways to get around the code and avoid the regulation that they were being put through. Click here for a more detailed description of the production code and its provisions.
The voluntary ratings system started with four ratings:
-G - for general audiences, all ages admitted
-M - for mature audiences - parental guidance suggested, but all ages admitted
-R - restricted, children under 16 will not be admitted without an accompanying parent or adult guardian
-X - no one under 17 admitted
Eventually, because of the perceived nature of the M rating, it was changed to GP (general audiences, parental guidance suggested), and then a year later to PG (parental guidance suggested). And later, the PG rating was split into two ratings, PG and PG-13, giving a greater level of separation for intensity levels. Also, the X rating became a much heavier rating than originally intended by the MPAA, so it was changed to NC-17, allowing parents to know that it was a movie that they would not want their children to see.
Along with the changes to the ratings themselves, the way that they were used were revised as well. Instead of just being a letter to look at and make a blind decision on the movie, along with the ratings was put a description of why the movie was rated the way that it was. This allowed parents to make more educated decisions on the type of movies that they would permit. A full description is now available to anyone at each movie theater by phone or at the box office, in some movie reviews and also at www.mpaa.org.
Also, read a more in-depth description of the history of the current ratings system on the MPAA's website.