Ever walked into a store, spied a gorgeous handbag or a hot car and then been told it's the last one in the store? Or, in the case of a unique car, the last one in Australia? Most customers who have been thinking about the purchase anyway are likely to grab the opportunity to buy the last item. That's because scarcity has a big impact on the purchasing decisions of customers.

That's what social psychologist Dr Robert Cialdini espouses in his lectures and books. He's written Influence: Science and Practice and Influence: The Psychology of Persuasion which is based on research into why people comply with requests in business. If you get a chance to listen to some of his podcasts (there are a couple available on iTunes), it's a fascinating insight into how and why customers buys.

The value of scarce opportunities
Cialdini gives the example of when he was in a traffic jam while travelling in the United Kingdom. On that day, an extra 300,000 cars were on the M4 Motorway, many of them circling Heathrow airport. The reason? That day was the last landing of the Concorde. He points out: "Something that had happened twice a day for many years wasn't of interest until it was the last one - until it was a scarce opportunity - and then it acquired value."

The implication for business is that if your product or service has a unique offering, it's important to highlight this or point this out to prospective customers. If you are few items left of a particular product, it's worthwhile to bring this to their attention. This can be done via signage in your store, an alert on your website - or simply verbally when you chat to customers.

Cialdini says: "If we have an idea of proposal or program that has unique or uncommon features, we would be fools if we did not raise the uncommon features to the consciousness of our audience."

How can it work for you?

You could take this further in your marketing - perhaps in your brochures, newsletters or other communication with customers. If you have a particular product you are promoting, you may even keep customers updated with how many are left by sending an email - or having a tally in the store - with a running (decreasing) total of what's left. This is also a good way to hold a "clearance sale", also informing customers that once the stock is gone, it will not be replaced.

This approach is obvious for people who sells products but it can work equally well for service businesses. You might be a professional services firm but choose to limit the number of clients you want to work with. Make this clear and you might have prospects clamouring to be one of your clients!

Maybe it's time to think about how you can use scarcity in your marketing efforts?