The Friday File: Since 1968, the Motion Picture Association of America has rated movies. Studios seek movie ratings because major theaters will generally not show unrated films. In 1984, the PG-13 rating began. Since then, very few G or (dreaded) NC-17 rated films have been released. PG-13 movies have numbered about 100/year, PG movies have averaged about 150/year, and R rated, about 400/year, well over half of all rated movies.