Fewer appeals have been filed in recent years over ratings decisions rendered by the MPAA, according to a new report by the trade organization marking the 50th anniversary of the ratings system.

Introduced on November 1, 1968 by Jack Valenti in the wake of films such as Who’s Afraid of Virginia Woolf? causing a stir with their provocative content, the ratings system has assigned letters to 29,791 films as of September 30.

Of those nearly 30,000 films, 17,202 were rated R, while just 1,574 have been rated G for general audiences.

A total of 428 films since 1968 have appealed the initial ratings decisions, with fewer than 1% succeeding in getting the rating overturned. Some of the cat-and-mouse exchanges over films such as South Park: Bigger, Longer and Uncut, American Psycho and Natural Born Killers have attained near-mythic status in the industry and popular culture.

In 1984, the year that the PG-13 rating was introduced, 18 films (6% of the total number rated that year by the MPAA) appealed their ratings. Over 50 years, the annual average is nine appeals. Since 2010, though, just five films a year have filed appeals. In 2016, just a single appeal was filed, and it was rejected. The report does not draw any conclusions about why fewer films have appealed their ratings.

Along with the survey of ratings, the MPAA also released a digital archive of documents charting the creation and rise of the rating system as well as that of the Hays Code, which preceded the MPAA ratings. The group also put out answers from the Classification and Rating Administration in response to frequently asked questions.

“We often find that when people have problems or issues with the ratings, they are based on misconceptions about our purpose and role,” said Joan Graves, Chair of CARA and a senior VP at the MPAA. “It is our hope that with the release of these materials, we can promote a greater understanding of how the MPAA ratings serve parents, young audiences, and filmmakers alike.”

MPAA chief Charles Rivkin said the 50th anniversary milestone “feels particularly hard-earned and special” given the many ways that society, culture and Hollywood have changed over the past half-century. “We could point to many factors behind the ratings’ success,” he said, “but the clearest one of all comes directly from our founding mission: to maintain the trust and confidence of American parents.”