One of the 60th anniversaries that will go largely unnoticed this year is New Zealand economist Bill Phillips' invention of an economic calculating device called Moniac.

The Moniac is an ingenious proto-computer that promised to predict scientifically a nation's economic fortunes. It opened and closed valves that released water into tubes, demonstrating the consequences of a downturn in consumer spending, for example, or a rise in interest rates. It's the big and bold work of a bonafide genius ... and it doesn't work. That's because all economic forecasts are subject to x factors - or 'events' as they are better known.

Today, globalisation has consigned any national economic calculator to history. Now a rogue trader in France, playing around with tiny transactions on the world's markets, can run up a $7bn debt. And the selling of mortgages to down-at-heel Americans who were unlikely ever to repay them can be the catalyst for a worldwide recession.

The Moniac is a reminder never to take numbers - however logical and accurate on their own terms - as gospel.

That brings us to ShoWest which, appropriately given its Las Vegas setting, churns out huge quantities of grand figures (the old joke springs to mind about 75.2% of statistics being made up).

The biggest of the figures is the $9.6bn all-time record domestic box-office takings stat. But in a credit-crunch climate, the temptation to look beyond the veneer becomes a positive obligation.

The neon elephant in the Vegas casino is the issue of profit. If those enormous box-office takings were achieved with margins that make them sustainable and attractive to investors, then great. If not, then one starts to question other core assumptions. In a week of gloomy forecasts, chief among those questions is how the industry will weather a global economic crisis.

Not surprisingly, at Showest the trick is to talk up the business - and there's much to boast about. But the recurring theme that film is recession-proof deserves closer examination than it seems to be getting.

It's true that in previous recessions film has coped pretty well.

During the recession of the 1930s, the silver screen provided a welcome distraction from many of life's problems, such as putting food on the table. One could make a similar argument for the early 1990s downturn in which, again, cinema tickets were cheap compared to other forms of entertainment.

It's worth noting how much has changed since the recessionary year of 1991. It seems so recent, yet since then the mass market has welcomed the internet, iPods, DVD players, games consoles, satellite TV and mobile phones. Cinemas have mostly morphed into multiplexes, which now often require a journey by car because of their out-of-town locations. Add on babysitters and the perceived value of the ticket price might be more testing than the industry thinks, in comparison to home entertainment.

But what's also changed is the importance of DVD to the economics of film, and here again the picture is cloudy. Having finally won its battle to dominate the next-generation DVD market, Sony's Blu-Ray format now faces a struggle to convince a consumer market watching its pennies to adopt what remains to the public a replacement technology.

That's bad news for the wider industry or potential investors. This is not a pessimist's charter but a warning against complacency. The industry cannot allow itself to be blinded by big numbers, as the over-reaction to the 2005 box-office collapse demonstrated.

One of the less-attractive traits of modern languages is to turn phrases and nouns into verbs, but we should make an exception in the current climate. The industry is not innately immune from economic misfortune and needs to 'recession-proof' its offerings, whenever possible.

As Universal's David Kosse pointed out at ShoWest, that means using new technology to engage with audiences; it means embracing digital change and aggressively adopting and marketing the benefits it can bring; and it means ensuring the economy of film is geared to producing excellent product for clearly defined audiences.

Grand figures are just fine for external consumption, but let's keep the Moniacs in the museum.