October 7 marks the date the Motion Picture Association of America (MPAA) adopted the film-rating system they still refer to today.

Back then, movies were rated G, M, R, or X. Of course, the M later became the PG we're used to seeing today.

Over the past 45 years, the ratings system also came to include the PG-13 rating in 1984.

In honor of the anniversary of the film-rating system, we've compiled the highest-grossing R-rated movies.

Because they play to a smaller audience, R-rated movies usually don't earn anywhere near as much as PG-13 films do.

"Ted" became the highest-grossing R-rated comedy last year after its theatrical release. A sequel has been announced for 2015. Universal It's rare that you'll find an R-rated movie make the list of highest-grossing movies at the end of the year.

Last year, 187 R-rated films brought in $2.9 billion at theaters. Compare that to the $5.6 billion 124 PG-13 films made in ticket sales.

"Ted" snuck onto the list last year earning an impressive $549 million worldwide.

What other R-rated movies have soared at the box office?

Here are the highest-grossing R-rated movies worldwide:

Note: the following numbers do not account for inflation.

1. "The Matrix Reloaded" (2003): $742 million

2. "The Passion of the Christ" (2004): $611.9 million

3. "The Hangover: Part II" (2011): $586.8 million worldwide

4. "Ted" (2012): $549.4 million

5. "Terminator 2: Judgment Day" (1991): $519 million

6. "Saving Private Ryan" (1998): $481.8 million

7. "The Hangover" (2009): 467.5 million

8. "The Matrix" (1999): $463.5 million

9. "Pretty Woman" (1990): $463.4 million

10. "Gladiator" (2000): $457.6 million

11. "300" (2007): $456 million

12. "The Exorcist" (1973): $441.3 million

13. "Terminator 3: Rise of the Machines" (2003): $433.4 million

14. "The Matrix Revolutions" (2003): $427.3 million

15. "Django Unchained" (2012): $425 million

And here are the top ten domestic releases:

1. "The Passion of the Christ" (2004): $379.8 million

2. "The Matrix Reloaded" (2003): $281.6 million

3. "The Hangover" (2009): $277.3 million

4. "The Hangover: Part II" (2011): $254.5 million

5. "Beverly Hills Cop" (1984): $234.8 million

6. "The Exorcist" (1973): $232.9 million

7. "Ted" (2012): $218.8 million

8. "Saving Private Ryan" (1998): $216.5 million

9. "300" (2007): $210.6 million

10. "Wedding Crashers" (2005) $209.3 million