An anonymous Chris Anderson reader reveals how Hollywood hides the fall of the hit:
I happened to be riding to work with an exec from one of the major studios this morning, and he mentioned that the studios are increasingly making deals with theaters to inflate opening numbers. In particular, they will give the theaters very high revenue share for the first X days of the movie (he mentioned 100% for the first 3 days), incentivizing the theater to maximize the number of screens the movie's shown on, inflating opening numbers.
The particular example of Superman and Pirates were actually the ones he brought up - that Superman's decline was partially due to the theathers' incentive period running out.
(Via JC Yuviengco.)