I want to introduce you to my plan. My latest wheeze. I am going to raise one billion pounds for charity. A year. Every year. For the rest of my life. Well, not exactly me, all by myself. That would take ages. I am going to do it with a mate.

And now I am going to tell you how.

Let's begin in Bridgend and the sad story of baffling teenage suicides. Can it really be true that these young people took their lives in order to imitate each other? Unbelievably, it could be. It is impossible to know exactly what motivated these particular individuals. Yet if these were copycat deaths it certainly wouldn't be the first time such a thing has happened.

In his book The Copycat Effect, the suicide prevention expert Loren Coleman records numerous occasions over the past 300 years when the suicide of a prominent public figure has been followed by a bulge in the number of suicides. Coleman records, for instance, that there was a 12 per cent rise in suicides in the month after the death of Marilyn Monroe. And this was not followed by a matching decrease later. The total went up.

One other feature of this increase is particularly striking - the similarity of many of the deaths to Monroe's own. There were 197 suicides in that month in the US that corresponded closely to that of the film star. Here's the thing - mostly young blonde women.

This is the reason why in the internet age we might see more of this sort of behaviour. In the past, young people might imitate a celebrity suicide - Monroe or, say, Kurt Cobain - that they read about in the newspaper. That is because they relate to these public figures, feel they are just a little bit like them. But think how more powerful the impact might be when the death is of one of their peers, someone more like them. The internet allows peers to publish - it spreads information among members of the same social group. In these circumstances we are almost bound to see an increase in copycat behaviour.

Fortunately, people won't generally be copying each other's suicides. Much of the time we follow each other in small ways, and don't even realise we are doing it. In his interesting book Herd - a study of our behaviour as a group - Mark Earls notes the evolution of informal rules guiding where to

stand in the men's urinals. If a man is able to, for instance, he will always leave a one urinal space between himself and the next man. And he will stand one metre behind the stall while waiting to use them. Nobody has ever discussed this, we simply watch each other and do as others do.

The more we know about the behaviour of others, the more we are likely to follow it. A famous experiment conducted by the social psychologist Solomon Asch shows this clearly. Individually his subjects managed to answer a simple test question correctly. But when told that most others had given a different (and incorrect) answer more than one third of them changed their minds and copied the error.

It is always said that we love an underdog. Nothing could be farther from the truth. We love the favourite. We move over to be on the favourite's side as quickly as we can. Politicians are familiar with this. That's why they spend so much of their campaigning time saying that they are winning. The teams behind Hillary Clinton and Barack Obama both tell journalists that they relish underdog status. But it's pretty impressive how much energy they devote to showing that they are really on top, now isn't it?

There are two implications of all of this for public policy. The first is to stop doing harm. What do you think happens when you announce that teens are all out on the street binge drinking? Asch gives you the answer. More binge drinking. You are normalising a behaviour you should be isolating.

What happens when you announce that there is an obesity epidemic and that everyone is getting fatter? That's right. People learn that if they put on weight they are far from alone. Jamie Oliver's school dinners television programme lambasted Turkey Twizzlers, making them infamous. Sales promptly rose by 32 per cent.

The idea that we need to understand social norms and stop doing harm formed the centrepiece of a recent speech by the Shadow Charities Minister, Greg Clark. And he is the mate with whom I intend to raise the billion pounds a year.

At a conference organised by the Centre for Policy Studies, Greg asked the audience how much they thought it appropriate to leave as a tip in a restaurant. Everyone had a view - answers ranged from 10 to 15 per cent. Leaving a tip in an eaterie to which we may never return is an odd thing to do really, but we all acknowledge the social norm and almost all abide by it, even when no one else is looking.

Then Greg asked this - what proportion of your salary should you give to charity? There was a confused silence. Nobody knew. There isn't a social norm.

Now estimates of how much we do give to charity vary. One survey suggests it is as low as 0.5 per cent on average. But the most widely accepted figure is that provided by the Charities Aid Foundation - 0.73 per cent. Greg provided the audience with the result of a simple calculation. If the average could be raised to 1 per cent it would bring £4 billion a year into the coffers of charities.

That would be far more useful to charities than anything that could be achieved through politics or changing the law.

So the idea, the wheeze, is this - to create a new social norm, in which people feel they should give at least 1 per cent of their income to charity. Even if it only partly succeeds, it could raise £1 billion a year at least.

This isn't about persuading people to give money in the usual way - through exhortation and so on. It is simply about spreading the idea from peer to peer that decent people, people like you, people in your circumstances, people you admire are all giving at least 1 per cent. And if you wondering how much you should be giving, that's roughly the right amount.

It could work, couldn't it?

daniel.finkelstein@thetimes.co.uk

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