What makes us all so depressed is all this liberal capitalism, the market system that showers us with cornucopian amounts of wealth and choice. At least, that’s the remarkable claim in the book Affluenza by the clinical psychologist Oliver James.

Can he seriously support the idea that the English-speaking nations, living as high on the hog as any group of humans have ever managed to do, are as a result sunk into gloom, doom and despondency? He points to the Danish, who have been found consistently to be one of the happiest groups on the planet. But as the British Medical Journal reported recently, the Danes have extremely low expectations and are thus pleasantly surprised when something does happen — a useful survival adaptation in a country where just about everything except the daily bread is supplied by a state bureaucracy.

This is not quite what James means, however. His thesis is rather that the glaring inequalities produced by market capitalism, unassuaged by eye-wateringly high tax rates and social redistribution, are exactly what make us all mad.

We are asked to observe the United States, where fully 26.4 per cent have suffered mental illness in the past 12 months, six times the prevalence in either Shanghai or Nigeria. That China spends 5.5 per cent of its GDP on healthcare while the US spends 16 per cent, thus having far more people available to diagnose it, seems not to matter; nor that such spending could mean a touch of the glums being treated as illness. Nor the somewhat unkind observation that with a life expectancy of 47 years Nigerians could be too busy dying to get depressed.

But the assertion that it is inequality that causes the madness is what appears to be — if I can use the word — insane. Economists measure inequality using the Gini coefficient. A value of one means that one person has everything, the others nothing, while a value of zero means the equality of the grave. Denmark does have a low one by international standards, 0.247; the UK 0.36, the US 0.408. However, in a small problem for James, that for China is 0.447 and that for Nigeria is 0.506 (all World Bank figures, 2004).

So if we leave aside the Danish result (what we might call the bigotry of low expectations, if that phrase were not already used to describe our education system), the actual evidence that James presents shows us that increased inequality makes us happier. We in the English-speaking nations are, in fact, too egalitarian to be truly happy.

Contrary to his desire, therefore, James has shown that we should reduce redistribution, take the shackles off the capitalist juggernaut and find greater happiness in admiring the rich and successful from our hovels.