> It's very easy to see that this trend has developed and accelerated over the last 30 years. In 1981, 7 out of 10 of the year's top-grossing movies were original material. In 2014, it was 1 out of 10.

The best reason for this I've seen is repeated material plays well in the Asian etc markets. The initial movie becomes essentially an ad for the squeals.

Because of the huge copyright infringement in these markets, ads are to expensive to run to the whole population to get them to the movies.

But once the first movie is out the profit by sheer numbers in these markets on squeals makes it worth while.