It has happened slowly and with little fanfare, but a look through the weekly listings for new film releases reveals that a big change has taken place in Hollywood. The blockbuster action movies and romantic comedies that used to dominate the screens of US multiplexes have been joined by an unlikely genre: documentaries.

The popularity of non-fiction films has exploded, thanks to filmmakers such as Michael Moore and the Oscar success of An Inconvenient Truth, the call to action on global warming from Al Gore. An influx of money from wealthy philanthropic patrons has boosted the number of documentaries being produced to the extent that there are now more in the pipeline than ever before for release in cinemas and on pay-television channels. The act of investing money in movies with powerful social messages has even spawned a new term: “filmanthropy”.