Is Hollywood's sequel bubble about to burst?

There have already been 16 sequels released in theaters so far this year. Everything from "My Big Fat Greek Wedding 2" to "Now You See Me 2" to "The Conjuring 2."

In addition, there are quasi-sequels like "10 Cloverfield Lane" and sequels that take place in a bigger universe like "Batman v Superman: Dawn of Justice" and "Captain America: Civil War."

It's almost as if Hollywood is in a sequel bubble, much like the housing and tech bubbles that eventually popped.

It wasn't always this way. When the original "Independence Day" opened in theaters 20 years ago, not one of the top 10 domestic films that year was a sequel.

And while sequels have always been a part of the film industry, the last few years have seen a surplus.

Since 2010, at least half of the top ten films each year have been sequels. Last year saw seven sequels in the top 10 including "Jurassic World" and "Star Wars: The Force Awakens."

While some sequels like last weekend's "Finding Dory" have been hits, there have been plenty like "The Divergent Series: Allegiant" and "Alice Through the Looking Glass" that have flopped.