Per my many past posts on the subject, a great chart showing how flat domestic US box office is (hovering around $10B mark), while DVD sales have come and gone and Blu-Rays aren't filling the gap as Internet- and cable-delivered (virtually indistinguishable when it comes to the home) take over with their much-thinner margins (none of that being shown on this Economist chart).
Thus, why it's so crucial to Hollywood that foreign B.O. has more than doubled in last decade, and shows all signs of taking off even more.
Why? As with most things, it's the emergence of the global middle class. Think to when movies took off in America (1920s) and then realize how sustaining they were even during the Great Depression (escapism), thus all bottom-of-the-pyramid logic plays here too.