The two highly anticipated new episodes of Star Wars have been criticized as disappointing, having a stupid script and over-dependent on computer effects. Reviewing past Hollywood movies, it is quite often that the second or third episode has much lower quality, even if the production crew is the same (personally, I will take Jurassic Park 3, Alien 4 and Men-In-Black 2 as examples). Why is this the case?

To solve this mystery, we need to know when in what circumstances will there be a second episode of a movie. The story of a movie is not what determines if the movie would have a second episode or not, because almost all Hollywood movies have an ending implying the possibility of a second episode. Plenty of dinosaurs are still alive in the end of Jurassic Park, which eventually leads to Jurassic Park 3; yet there is not another episode for Gorzilla, which has a comparable ending. Frankly, the real determining factor is how much money the movie has made. A rational filmmaker would not invest in the second episode of a movie that resulted had lost money. It should not be surprising that the first episode of a movie series is always the blockbuster of its year.

I believe the real reason behind the decline of a series is regression to the mean. The problem here is that to be a blockbuster of the year (out of the hundreds of other films being produced in that year), a movie must be exceptionally good. And to be exceptionally good intuitively implies exceptionally better than average. It should not be surprising then when we find the second episode of a movie worst than the first; they are just either doing average, or only slightly better than average. Honestly, the new Star Wars movies are still better than most of the movies in their respective years. The second episodes are not too bad; it is just that the first episodes are too good.