The principle of scarcity states that people value something more if it is in short supply; perceived value has an inverse relationship to availability.

Some things are valued because they are useful, beautiful or powerful. And others are valued simply because they are scarce. Minerals such as gold and diamonds hold their value because they are so rare; all the gold ever found would fit into a 150ft cube.

For the purposes of persuasive copywriting, using scarcity means emphasising that your product or service (or something about it) is scarce or restricted in one or more of these dimensions:

Quantity

Only a few exist, or are available. Examples: ‘limited edition’ products, ‘collectors’ editions’.

Just 500 of these beautiful limited edition Star Trek commemorative plates have been produced.

Easyjet uses temporal scarcity to persuade travellers to act

Time

Only available within a limited time window. (See image)

Fantastic sale must end 31 January!

Competition

Other people might get there first. Most likely to be used in conjunction with another dimension of scarcity.

Demand for this unique cruise is sure to be intense. Act now to book your place before the May 30 deadline!

Threat

The opportunity will be taken away permanently if you fail to act.

Post Office closure plans are based on usage patterns. So use your local PO – or lose it!

Profile

Only available to certain prospects or existing customers. The group can be defined on the basis of age, buying history, geographical location or any another attribute.

As someone who’s previously bought Lawnmower World, you’ve been selected to receive details of this incredible subscription offer…

Invitation

Only available if an existing customer invites you.

Spotify Free is currently in an invitation-only beta, which means you need to have received an invitation token to access the service.

Scarcity derives its psychological punch from two sources: loss of freedom and fear of regret.

As things become more scarce, we progressively lose freedom – and we hate to lose freedoms that we already enjoy. In our context, marketing and advertising, a product that was previously freely available is suddenly restricted somehow. We react against that by trying to grab it and keep hold of it (i.e. by buying it).

At the same time, we have a strong fear of regret – that is, an anxiety that acting (or failing to act) in a particular way will bring us remorse when it turns out to be ‘wrong’ after some irrevocable future event. If the fear of regret is strong enough, it becomes easier and more desirable to spend money on a purchase than to risk regretting not buying. Buying is effectively an insurance against feeling bad about not buying in the future – a psychological investment. And it may have little or nothing to do with the tangible benefits provided by the product.

To use scarcity, simply invoke whichever of the dimensions listed above are applicable to your product, service or promotion. Scarcity is often used to add impact to calls to action – telling the audience what to do while giving them a powerful reason to do it right now.

Of course, it may be that your product or service isn’t actually scarce in any way. In fact, it’s very likely you want to sell it to as broad a spectrum of people as possible, and manufacture or deliver it in massive quantities in order to realise economies of scale. But you still might want to artificially invoke one of the scarcity dimensions above in order to make it feel rare and desirable.

For instance, the ‘invitation only’ launches of Google Wave and Spotify made them feel exclusive and exciting. However, the actual number of invitations is infinite, since each new invitee is given ten invitations to hand out.

If you’re going to use scarcity, it’s important to remember that people aren’t stupid. A ‘limited edition’ that’s clearly mass-produced, with no numbering of individual editions, isn’t going to be that compelling. A time window that’s endlessly extended, like those shops that are forever having ‘closing down sales’ and then returning to normal trading, will soon lose its power to motivate.

The principle of authority states that people defer to experts, and are more likely to accept a suggestion if it is backed up by authority.

Once upon a time, adverts could get away with making big, bold claims about their products and have them accepted at face value. Slogans such as ‘Guinness is good for you’ and ‘Guinness for strength’ (illustrated) just came right out and stated a (perhaps contentious) benefit based on the advertiser’s own authority. In a slight variation on the theme, washing-powder adverts used an off-screen ‘voice of God’ to the on-screen housewife, putting her right about her choice of Daz vs Persil.

Guinness makes a bold claim in the days before the ASA

Over time, people grew more savvy and wouldn’t accept advertisers’ own words as gospel. So they had to bring in third-party ‘experts’ to back up their claims. This is still going strong today, with ads for toothpaste, shampoo and cosmetics presenting ostensibly impartial scientists, stylists and make-up artists to endorse the product. The underlying message is ‘do what the experts say’.

Sometimes, the authority isn’t a ‘real’ authority, just someone who’s likely to be regarded as authoritative – as in Carol Vorderman marketing Benecol in the late 1990s. She wasn’t a nutritionist, but in the public mind she was clever, wholesome and trustworthy.

So, invoking authority has a long and distinguished history. Does that mean it won’t work today? Absolutely not. As long as you use an authority that the audience actually respects, you can still persuade the audience very effectively. Some examples of authorities you could use (with potential products/services in brackets) include:

• Scientists
• Industry bodies
• Newspapers or trade journals
• Government studies
• Reports, surveys and statistics
• News items

Basically, you’re looking for any material produced by an impartial authority that will back up your sales message. For example, it’s easy to see how eConsultancy’s trends and innovation reports could be used by online marketing firms to push their own service portfolios to potential clients.

Of course, if your audience is modern and tech-savvy, they may not take your word as gospel – or even the word of of a third party. Instead, they’ll go online to get the unfiltered, unvarnished truth, in the form of what other people are saying about you. For example, the typical Amazon user will probably glance at the official review and a third-party (e.g. newspaper) review, before focusing most of their attention on other users’ views. B2B service providers can collect and use customer testimonials in their marketing, as well as inviting reviews on various networking and directory sites.

Gradually, these shared user opinions have moved from the margins to centre stage. Their credibility has grown to the point where it’s eclipsing traditional authorities. Journalists have begun to establish the credibility of a ‘backlash’, ‘movement’ or ‘trend’ by pointing to the number of Tweets or Facebook groups about it, or including quotes from forums or blogs in their reports.

In an attempt to capitalise on the trend, cutting-edge initiatives like first direct live provide a snapshot of the social-media buzz (both positive and negative) about a brand. The idea is to appear open and honest, while also allowing the authority of real opinion to do the selling for you.

This approach can work, but it’s important to consider some key questions:

• Does your audience know and understand social media?
• Will they attach any weight to social-media coverage?
• Does the user-created content about your brand have sufficient depth and detail to sell your product or service?
• Is the balance of opinion reasonably likely to be positive?

If you’re happy with the answers, it could be worth invoking ‘social authority’ by incorporating social-media content into your marketing efforts.

Consistency is a very useful ploy in face-to-face negotiation. In my last post on persuasive copywriting, I mentioned an RSPCA canvasser who deftly used social proof to guide me towards a decision to donate. But at the start of the conversation, she’d also asked me whether I was an animal lover. I answered ‘yes’. (Would anyone say ‘no’?) The appeal for donations followed on from this, with the implication that refusing to give would be inconsistent with my stated position. Similarly, TV appeals count on people’s consciences making them follow through on their telephone ‘pledges’.

Copywriters, of course, aren’t in a dialogue with those they wish to persuade. But they can still ask questions that encourage the reader to commit to a position, albeit mentally, and use that commitment as the basis for a persuasive message.

Ben Affleck explains the principle of consistency to Giovanni Ribisi in Boiler Room

In the film Boiler Room, there’s a great scene where Ben Affleck’s character exhorts his trainee stockbrokers to sharpen up their phone selling. He implores them to ask any question, however rhetorical or ridiculous, just to get a ‘yes’ from the prospect. ‘If you were drowning and I threw you a lifejacket, would you grab it? Yes! Do you want 30–40% returns? What’s he going to say?’ (Click here to watch the clip, which contains strong language.) By saying yes to something – anything – the potential customer implicitly aligns himself with the seller.

This is why utterly clichéd headlines like ‘Do you want to save money on your home insurance?’ achieve useful aims: they elicit a positive response from the reader. They also provoke thought, generate active involvement and encourage personal identification with the product. From that platform, the copywriter can go on to build a case for the product or service they’re promoting, using the audience’s (tacit) commitment to their position as the foundation for their persuasive argument.

It’s also easy to see how consistency could be used to promote an upselling proposition, such as continuing with a magazine subscription. You subscribed, you enjoyed the magazine or found it useful, so why not continue? (Silent implication: because cancelling, having read and enjoyed the magazine, would be inconsistent.)

The most famous examples of social proof in copywriting are headlines along the lines of ‘Ten million housewives can’t be wrong’, which position a product as the preferred choice of the majority – and therefore of the reader too. It is, of course, a non sequitur – the argumentum ad populum (‘appeal to the people’) that suggests that if lots of people believe something, it must be so.

The King deploys the argumentum ad populum on the cover of his 1959 hits compilation

A classic and much-used example is selling a product on the basis of its being the number-one seller, or promoting a company on the basis of its being the leader. The saying ‘nobody got fired for buying IBM’ encapsulates the appeal of going with the majority.

Social proof can have quite a powerful emotional sting. Recently, a door-to-door canvasser for the RSPCA told me that ‘lots of people’ in my ‘animal-loving neighbourhood’ had signed up for regular donations. The inference being that if I didn’t, I’d be some kind of animal-hating outcast.

In the examples above, the copywriter is actually imparting the information to support their position. But in the age of Web 2.0, the consumer is much more likely to go out and find such information for themselves. If customers want to know the views of their peers, they don’t have to look much further than Twitter, Facebook, Amazon, the iTunes store or any of the myriad other channels where consumers share views and information. As a result, marketing messages have less authority and may simply be disregarded.

However, there’s still room for copywriting based on social proof. Think about where your customers look for advice or guidance, and how you can emulate the tone or nature of that content. Testimonials and case studies are enduringly powerful, particularly in B2B marketing, and they allow the copywriter to shape, edit or subtly direct what is said so that it highlights the benefits of a product or service. In B2C marketing, there’s a clear trend towards using real or mock-real figures in TV advertising and elsewhere, or documentary styles, to give a sense that the reader or viewer is directly accessing the views of their peers.

As long as the information feels trustworthy, the audience will still respond – remember, many people actively desire the reassurance of running with the majority, so as long as your message is consistent and clear, it’s got a good chance of succeeding.

I am a hetero male. I like attractive women. Therefore I will buy this technology magazine

The principle of liking is clearly seen in adverts that deploy an attractive face to promote a product. Research shows that we generally like good-looking people more, and are more likely to respect their opinions.

Cialdini himself cites the example of Tupperware to illustrate the principle of liking in action: the product being sold in the home, face to face, via a warm, friendly relationship between vendor and customer. But copywriters, by definition, don’t get to meet their audience and strike up a friendship with them. How can we apply the principle of liking in copywriting?

One way would be to write a headline or introduction that sets up a friendly rapport with the reader. Instead of beginning with the benefits of the product or service (as we would normally do by default), we can subtly align ourselves with the reader by suggesting that we have things in common, or giving them a compliment. For example:

If you’re a parent, you already know how to manage your time, deal with difficult people and juggle priorities. Now here’s a way to get rid of at least one of your worries…

By demonstrating knowledge of the reader’s situation, we indicate that we are like them; that we understand them. And because we’re implicitly praising them too, we hope they’ll warm to us as a friend. Copy like this marks out common ground between the copywriter and the reader, using the reader’s recognition of details from their own life as the key. This sets the scene for a marketing message that, because it comes from someone who is both ‘like’ and ‘liked by’ the reader, is more likely to be acted upon.

Of course, it’s easy to get wrong. The setup needs to be convincing – which means writing it from first-hand knowledge or rock-solid research rather than a five-minute scan of a Wikipedia page. It also needs to be sincere, insofar as a mass-communicated message can be sincere. (See my earlier post on sincerity, tone and attitude in copywriting.) The whole message needs to be congruent, with content, tone of voice and presentation all working in harmony.

There’s no need to do too much; often, a lighter touch works better. People will warm to those they have just met, as long as they feel there is some kind of link or common ground. Very small similarities or shared interests are enough to generate rapport. We know this from real life, where even the most distant common acquaintance will make us warm to someone we otherwise know nothing about.

Finally, note that while we like those who praise us, we dislike those who convey negative information. This ‘shoot the messenger’ tendency has important implications if you’re going to use scare tactics in your copywriting: by bringing bad news to the reader’s door, you associate yourself with it – even if it establishes your knowledge of their situation and you then go on to offer friendly advice.