The world around us of inequality.

Richard Wilkinson and Kate Pickett, academic epidemiologists at Nottingham and York universities respectively, are authors of The Spirit Level: Why More Equal Societies Almost Always Do Better.

They explain why fairly unequal societies such as Britain and the United States are more likely to suffer from a range of problems, including low life expectancy, illiteracy, stress, and a high crime rate. Even climate change is less of a challenge for a society with a narrow gap between rich and poor.

We in Britain are rich enough. Economic growth has done as much as it can to improve material conditions in the developed countries, and in some cases appears to be damaging health.

If Britain were instead to concentrate on making its citizens' incomes as equal as those of people in Japan and Scandinavia, we could each have seven extra weeks' holiday a year, we would be thinner, we would each live a year or so longer, and we'd trust each other more.

The authors point out that the life-diminishing results of valuing growth above equality in rich societies can be seen all around us. Inequality causes shorter, unhealthier and unhappier lives; it increases the rate of teenage pregnancy, violence, obesity, imprisonment and addiction; it destroys relationships between individuals born in the same society but into different classes; and its function as a driver of consumption depletes the planet's resources.

They use the information to create a series of graphs whose patterns look nearly identical, yet which document the prevalence of a vast range of social ills.

This has nothing to do with total wealth or even the average per-capita income. America is one of the world's richest nations, with among the highest figures for income per person, but has the lowest longevity of the developed nations, and a level of violence murder, in particular that is off the scale. Of all crimes, those involving violence are most closely related to high levels of inequality within a country, within states and even within cities. For some, mainly young, men with no economic or educational route to achieving the high status and earnings required for full citizenship, the experience of daily life at the bottom of a steep social hierarchy is enraging.

The graphs also reveal that it is not just the poor, but whole societies, from top to bottom, that are adversely affected by inequality. Although the UK fares badly when compared with most other OECD countries and is the worst developed nation in which to be a child according to both Unicef and the Good Childhood Inquiry, its social problems are not as pronounced as in the US.

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