No-one really knows what word-of-mouth is, whether it works or how to measure it. So what use is it, asks Leonard Klady.

There can be few businesses where the received industry wisdom is so often wrong. Or to be more diplomatic, by the time anything looks set as a rule, it's apt to be out of date.

And why should that be a surprise' One spends years, even decades learning the ins and outs of some possibly arcane aspect of the movies' art, science or commerce only to discover the world has moved on.

Yesterday's foolproof marketing strategy comes a cropper, a popular performer becomes unbankable. And then there are management changes that arrive like the Spanish Inquisition, wiping the slate clean rather than debating the assets and excesses it has inherited.

One area that's changed radically and may be going the way of the Great Auk is word-of-mouth.

For starters, it's always been an indefinable commodity. There aren't any real scientific studies as to how it works or translates to the movies; how many people need to see a film and tell others about it to have an effect on its future, good or bad'

In North America there's something called the exit poll. One company that routinely collars movie-goers as they leave the multiplex as a means of testing the temperature has what it calls the CinemaScore.

It is copyrighted, presumably to keep others from aping the methodology. That also might simply be a block to ward off prying eyes. Regardless, by the Sunday of a picture's opening weekend everyone in the industry knows whether it's scored an A+ or a B-.

Historically, that type of information hasn't really been informative. There is no direct correlation between a film's rating and its ultimate popularity. And as only a chosen few know the questions asked and how responses translate into a letter grade, it basically only serves to make one feel good or bad if the letter reflects on the initial box office.

Word-of-mouth, if it exists, is a consolation prize. As far as the industry is concerned, it's the fall-back to be called on when something doesn't work: a vague notion that can turn around the fortunes of a film struggling to find an audience.

Of course, that presumes word-of-mouth exists after the release and not leading up to an opening. So, let's call pre-release banter 'buzz'. For a movie where a production company has a major investment, orchestrating the conversation is critical.

If one spends a sufficient amount on advertising, and crowds print and electronic or digital outlets with bon mots from a film's actors and creatives, ideally there is no space for word-of-mouth.

The scenario is double-edged. It's presumptuous to assume anyone can control the entire conversation, for even in pristine lab conditions one has to take a breath. At that moment any interjection is going to alter the course of what will follow.

If it happens to be in a direction deemed unfavorable, one can simply throw arms in the air and allow word-of-mouth to take over. For as the man once said: 'He, who lives by the sword, dies by the sword.' Ouch!