In the back of Marketing magazine each week, a brand manager is asked a set of questions. one is 'how do you define marketing?' A recent reply is typical: "It's about creating, communicating and delivering an engaging, consistent and clear message to a target audience."

Grrrr… Since when did marketing just equal communication? Marketing has tradi­tionally been defined in terms of the four 'Ps': Product, Price, Promotion and Place. It's interesting how many marketing people nowadays seem to define their role in terms of 'promotion', or even more narrowly in terms of communication.

Communication is obviously important, but econometrics shows that the effects of the other three Ps are often even more important. here we focus on perhaps the least talked about P: 'place' – ie distribution.

Distribution is important in an obvious sense – people need to be able to buy you. But it's not enough to just be 'available'. Behavioural economics shows that people are incredibly lazy, and that all effort counts. The more widely and easily available you are, the more you sell. That's why Coke's aim is to always be 'just an arm's length away'.

Physical availability is also closely linked with what Byron Sharp calls "mental availability" or salience – the ease with which a product comes to mind. Many people find out about a brand by seeing it in-store, not on TV. Simply seeing the product on display is one of the simplest and most effective forms of 'advertising'. Which is why pack design matters so much. Shelf wobblers, gondola ends and all the other paraphernalia of merchandising help, but sheer ubiquity is probably the best way to ensure your brand is first to spring to mind.

As well as boosting salience, distribution can also create useful brand associations. By getting their brand into John Lewis' cafés, the makers of plum baby food not only brought their product to the attention of upmarket mums, but also sent out a clear signal about quality. Similarly, clever thinking about distribution can communicate things about value (selling your luxury car at a boat show, where it will look more affordable) or usage (displaying your sauce next to barbecue food).

Put all this together and distribution can have a big influence on sales. Econometrics regularly shows distribution tends to be the single biggest factor driving long-term growth for many brands.

Yet lots of marketing people see distribution as outside their remit. In many cases, it's the responsibility of a different department. This is a lost opportunity.

Thinking creatively about distribution can yield spectacular results, as companies such as Direct Line, Ocado and Apple have shown. And because very few brands have anything like universal distribution, there is nearly always scope for further growth this way, whether by harnessing new technology, like the Kindle or the iPhone, or thinking about old distribution methods in new ways, like selling headphones in vending machines or delivering parcels via corner shops.

Of course, distribution and communication are closely intertwined, as various IPA effectiveness papers have shown. Felix cat food is a good example. Over the past 20 years or so, advertising has helped Felix to gain distribution, both directly (by influencing retailers) and indirectly (by boosting rate of sale). This, in turn, has helped the brand to quintuple market share and boost ROI from advertising by 50%.

Digital marketing allows marketers to advertise their products and deliver them, bringing promotion and place even closer together. And with mobile marketing, the dream of being 'just an arm's length away' is fast becoming a reality.

More then ever, marketers need to exploit the power of distribution. few brands are so widely available that they cannot significantly increase sales through thinking creatively about it.

As JE Mars used to tell his colleagues: "the consumer is loyal to the brand they can find."

This article originally appeared in the June 2011 issue of Admap. Click here for subscription information.