After a phenomenally successful year - Japanese productions grossed an unprecedented $920m (Yen107.8bn) at the local box office in 2006 - the territory's film-makers and financiers are continuing their reliance on proven books, comics, manga and TV shows (known as 'gensaku').

Of the top 20 local films in Japan last year, 18 were based on existing properties: eight book adaptations, led by top earner Tales From Earthsea ($67m); seven based on manga (including animation or live-action franchises that began life as manga); two sequels based on TV programmes; and the song-lyric inspired Nada So So ($27.1m). Only two films, Suite Dreams ($53.2m) and Hula Girls ($12.3m), were original projects, the latter based on a true story.

Hits so far in 2007 have showed a similar reliance on the tried and tested. Dororo ($29.8m), Monkey Magic ($31.6m at time of writing), Unfair: The Movie ($24.5m) and Tokyo Tower: Mom And Me And Sometimes Dad ($15m), not to mention annual evergreens Pokemon ($31.3m) and Doraemon ($28.7m), have also drawn heavily from TV, manga and novels.

The dominance of adaptations of existing commercial properties has coincided directly with the wider growth of production consortia as a way of financing projects in Japan.

Originally the domain of animated films, a consortium approach was perfected by Studio Ghibli in 2001 with all-time box-office champion Spirited Away ($257m). Comprising Tokuma Shoten Publishing, Toho, Nippon Television Network (NTV), Dentsu, Buena Vista Japan, Mitsubishi and others, the consortium financed the film's $20m budget, extraordinarily high at the time.

As well as serving as a model of how partners can offset risk through shared investment, the consortium also showed how the partners' synergy can make the film a success. Partners for major releases typically include a studio, a distributor (which, in the case of Toho or Shochiku, is often one and the same), TV broadcaster and a publisher. There is often an advertising company charged with finding and securing investors with which to mount PR campaigns. Ad giants such as Dentsu and Hakuhodo are players.

It is now commonplace to see eight to 10 companies listed on a film poster. Talent agencies, production and post-production companies, music labels, newspapers and even toy makers are also often part of the mix, depending on the project. SFX houses are also getting involved - effects house Shirogumi is part of the production consortium for the CG-heavy Always - Sunset On Third Street films.

However, some producers and critics believe the cautious nature of consortiums is creating a deficit of riskier and more artistic films in Japan. And it is notable the Japanese films that have won overseas acclaim this year - Naomi Kawase's Cannes Grand Prix-winning The Mourning Forest and Masahiro Kobayashi's Locarno-winning The Rebirth - were original projects.