The summer ended today and it seems to have been a mediocre season for Hollywood. The total U.S. box office gross between Memorial Day and Labor Day was $4.3 billion, which is 1.4% less than 2008 but 4% above 2007 per Variety. At the beginning of the summer the box office was 24% above last year but it now stands less than a third.

So how did the year-over-year growth drop so much over 36 weeks? First of all Hollywood had an unusually strong first quarter and it was simply difficult to maintain such a large difference given the inherent volatility of movie attendance. Secondly the summer season is much more important; the average summer weekly gross is 40% more than other seasons. The summer is when the industry makes it or breaks it.

Lastly the 2008 summer was simply hot, with more stronger releases like The Dark Knight, grossed over $500 million domestically, as well as Iron Man and Indiana Jones and the Kingdom of the Crystal Skull which both made more than $300 million. So far this summer only one movie, Transformers: Revenge of the Fallen, has passed the $300 million mark. Looking forward the total 2009 box office is $7.4 billion which is 7% above last year so it should still be a strong year for Hollywood.

Update: Check out a Kim Master’s posting at The Daily Beast, “Hollywood’s Fake Math”,  which is a bit more negative in its assessment of the summer theatrical movie performance since it bases the comparison on tickets and not dollars.