As befits these recessionary times, there has been a noticeable shift of tone at the business end of the industry recently. New emphasis has been placed on the search for scientific, transparent, bona fide facts and figures that might impress an investor or bank manager. With risk-aversion now set in firmly, the spreadsheet seems to be taking prominence alongside the storyboard.

Yet the launch of the International Screenwriters' Festival in London - one of the best recent additions to the industry calendar - brought reminders of the limitations to market thinking.

Was there some kind of data or information that could guarantee success for film-makers or investors' Speakers including David Thompson, former head of BBC films and now at Origin Pictures, offered a few pointers to what was working now.

But the notepads of those hoping for that elusive winning formula quickly filled up with words such as 'magic', 'alchemy', 'luck' and 'timing'.

Olivia Hetreed, who wrote the screenplay adaptation of Girl With A Pearl Earring, offered the pleasingly Freudian description of film creation as 'getting into bed metaphorically with directors and making film babies'.

Best not to follow that analogy too much further down the biological track, but it's a very long pregnancy she's talking about. Given that a film might take from two to six years to come to fruition, it's pretty clear that serendipity is a big part of the deal.

Today's winning formula is tomorrow's old hat. Contrast that with the polar opposite discussion. The words 'recession-proof' and 'film' have become inseparable buddies. Tap them into a Google search and you will find something close to a million pages to peruse.

Film has become the exception that proves the economic rule, with a nice place on Easy Street while everyone else is moving to Skid Row.

There was a serious debate in serious newspapers this week about whether the Golden Globes should show off its finery in a time of economic trouble. Was dangling one's recession-proof bijouterie before the huddled masses not the very height of vulgarity'

So if film is on to a banker, why can't you bank it'

Firstly, of course, it's because the recession-proof, or at least resistant, part of the business is exhibition. People go to the flicks in a downturn because it's relatively cheap. The big studios get some of the benefits by taking big risks but further down the food chain, the lack of liquidity is a killer. So for most of the industry, the downturn is the same miserable fact of life as it is for any other sector.

But it's important not to mix up our crises here. The credit crunch came on top of existing challenges for the industry - the collapse of TV pre-sales, too much production for too little distribution, and so on. A lack of finance in the market, if one takes a Darwinian view, may help the industry by driving out weaker productions that have really had no relation to demand.

We also wallow too readily in this 'no-one knows anything' culture, which ignores the fact that, while there is no algorithm for success, there are business tools to improve opportunities and performance.

In a world where studios are owned by diversified multinational conglomerates and where banks have acquired a serious allergy to risky debt finance, the business has to find more practical commercial arguments.

That argument needs a command of business reality, fresh thinking about audiences and a healthy exploitation of that 'recession proof' cliche as a sound reason for investment. But there still needs to be a sprinkle of fairy dust.