What are the highest-grossing movie adaptations?

This week I have been looking at the 100 highest grossing films for each of the last 20 years. This gave me a dataset of 2,000 films with which to answer a question from Tom Worth...

Can you crunch the data on the number of films that are original screenplays and those that are based on some other source be it a book, comic, another film, etc. We all know Hollywood has gone franchise crazy recently but I'd be interested to see that actual data.

In summary...

• 51% of the top 2,000 films of the last 20 years were movie adaptations

• The most common source for movie adaptations is literary fiction.

• 2012 saw five times the number of sequels released compared to 1999

• Romantic Comedy is the genre with the highest number of original screenplays (79%)

• Only 16% of Musicals were original screenplays.

• 18% of Horror films were remakes

• Between 1994 and 2003, original screenplays outnumbered adaptations every year but one, whereas in the following decade (2004-2013) the opposite was true, with adaptations outnumbering original screenplays in eight of the ten years.

Original Screenplays versus Movie Adaptations

Across all films over the 20 year period, 51% of films were adaptations, 42% were original screenplays, and 7% were remakes.

Detailed Breakdown of Source

Looking at the sources of movie adaptations we can see that literary fiction was the most common, accounting for a quarter of the money made at the box office between 1994 and 2013.

Sequels

The number of sequels has grown considerably in the last two decades, from a low of 5 in 1999 to a peak of 26 in 2012.

Genre

I've left the most complicated chart to last. This shows the data split by the principal genre of each film.

Methodology

I used the Opus database to find the 100 highest grossing films in each year, in North America. I chose to focus on the domestic box office to generate the list as it appears to be more complete than international box office. The inflation adjusted budgets and box office grosses are to 2013 US$.