Something strange happened in East Germany when the Berlin Wall came down. Back pain had never been much of a problem there. But soon it was. It began to rise and rise. And within a decade of reunification, back pain was higher in East Germany than almost anywhere in the developed world. But there was one place where it was just as high. And when you find out where, you will be one step closer to understanding the postal strike.

You see, the planned postal strike needs a bit of explaining, doesn’t it? It is, at the very least, perplexing. In fact, I’d go farther. It seems, to use the careful terminology of political scientists, completely bonkers.

Here is a business facing a serious challenge to its very existence. Its management is installing new technology that will both strengthen the Royal Mail against its rivals and make life easier for its workers. Yet this investment is being greeted by strikes. Why? To advance a set of demands so vague that it is impossible to find anyone who can convincingly explain them, but simultaneously so unreasonable that it is impossible for management to yield to them.

The dispute is certain to be costly for everyone involved. It is not necessary to be a partner at McKinsey to appreciate that if Royal Mail staff disrupt the Christmas post, businesses will go elsewhere for delivery. If the Communications Workers Union cares to pay me a fee, I will draw them an organogram with an arrow flowing from their jobs to a scrap heap. (I thought I’d mention a fee, because, you never know, with their grasp on economic reality, they might just pay one.) Yet even if the Royal Mail keeps every bit of business and doesn’t lose a single job, the strike probably won’t pay. A study of strikes in the 1980s shows why. Economists from the London School of Economics found that the average increase in annual pay produced by strikes was only 0.3 per cent, while the average strike lasted 11 days. Each strike day, of course, costs the worker a day’s wages. The study concluded that the wage gain would have to be retained by individual employees for 30 years simply for them to break even.

It shouldn’t be necessary to use a study to remind postal workers of the trade-off between the gains from a strike and lost wages. It should be part of their collective memory, and that of their union. The miners may have beaten Ted Heath but, before that, Heath beat the posties. In 1971, their 47-day strike collapsed and they were forced to go back to work without even the increase they had been promised when the strike began. The union and the workers ran out of money.

So if the strike makes no sense when viewed as a business person, an economist or an historian, why is it happening? That’s where back pain can help our understanding.

A group of German researchers, working on the idea that lower back pain was a “communicable disease”, studied its prevalence among East German workers after the Wall came down.

They had already observed that back pain was more common among West Germans than, say, among British people of working age. And they wondered if this high rate would be replicated among East Germans once the two areas formed a single community. And indeed it was. The economies harmonised, the political environment harmonised, back pain harmonised.

This study features in a striking new book called Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives, by Nicholas Christakis and James Fowler. The spine of the book is the mining of an extraordinary resource — the Framingham Heart Study. Thousands of residents of Framingham, Massachusetts — the large majority of them — signed up in 1948 to a biennial medical investigation that, remarkably, is still going on.

The authors discovered that the study administrators had kept a meticulous record of the social connections, the friends and family, of participants to be sure that over the years they would be able to track down those they were studying.

And, Framingham being a close community, most of these connections were themselves part of the study. This administrative practice and the basic study data allowed Christakis and Fowler to link the health, behaviour and attitudes of an entire social network.

Their findings were remarkable. The smoking of one participant raised the smoking level among his friends, his friends’ friends and his friends’ friends’ friends. Obesity followed the same pattern. And happiness did too.

Perhaps you need an example to show how surprising this is. At a family bar mitzvah at the weekend, I was explaining to my brother-in-law Michael that, given my social network, Christakis and Fowler would be against Michael’s cousin eating another profiterole because it would be bad for Anatole Kaletsky’s waistline.

The Framingham data provides the strongest statistical support we have yet had for an idea that social psychologists have held for some time — that members of groups “catch” behaviour from each other. Connected argues that this is particularly the case where networks are tight and where links with other networks are weak.

The postal workers union forms a classic social network of this type. However little sense striking may make to an individual, the idea that it is the right thing to do has spread round the group until everyone in it thinks that it makes sense. This is why the union is so resistant to the hiring of non-union labour to help to clear up the backlog of post. They fear that their mere presence will undermine the strength of the network.

The network effect is accompanied by another psychological quirk. A study of university fraternities showed that the more painful the initiation rites to the chapter, the more members value their membership. They have to do so to rationalise the ordeal that they have been through. Strikes work in the same way. Instead of the resolve of strikers weakening as the costs mount and the whole things becomes uneconomic, resolve strengthens.

If the Royal Mail dispute were about individual postal workers and their economic interest, it would be easy enough to solve. It could be ended in a conciliatory way with most people better off. Unfortunately things aren’t that simple. This is about the power and coherence of a group, and a group’s resolve. The sad truth is that the dispute cannot be ended until the group is broken.

daniel.finkelstein@thetimes.co.uk

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