Evidence based politics

The Spirit Level may be the most significant book I have read in 10 years.

Many people, myself included, hold to the ideological belief that social justice is a prerequisite for a truly democratic, peaceful, sustainable society. What Richard Wilkinson and Kate Pickett provide in The Spirit Level is the evidence to back up the belief.

When we look at the wealthiest nations, despite the inordinate wealth we find many health and social problems. While it is clear that the prevalence of these problems is hugely variable from one country to another, the evidence shows quite clearly that it is not the level of income in the different countries that is correlated with health and social problems.

Wilkinson and Pickett show – with detailed consideration of a mass of data covering 23 wealthy countries, ie those with a national income above US$25,000 per capita – that the prevalence of health and social problems is greater in countries with higher income inequality.

The evidence

Data covering a wide range of issues are considered in the book, including: the level of trust for other people, incidence of mental illness, incidence of drug and alcohol addiction, life expectancy, infant mortality, incidence of obesity, levels of children’s educational performance, homicide rates and imprisonment rates. These data are all publicly available from national and international agencies, so that there can be no accusations of cherry picking data.

The correlations between these problems and income inequality are generally strong, and the finding is reproduced within the USA when data collected at the state level is analysed – states with a greater degree of inequality have more health and social problems. Aha! you might think – correlation is not causation. Wilkinson and Pickett are experienced researchers and they are fully aware of this point. Much of the book is devoted not simply to presenting the data but to investigating the cause and effect relationships that might underlie the statistical evidence.

If you wish to view the evidence presented in the book yourself, it is available in a slideshow here.

The conclusions

There are a couple of very important conclusions that follow from Wilkinson and Pickett’s work.

1. Equality benefits everyone, not just the poorest. The measure of income inequality used in this study is not a comparison of the greatest extremes, the wealthiest 1% and the homeless, for example. It is much more representative of society at large – the measure used is the difference between the average incomes of the wealthiest 20% and the poorest 20% in each country. The degree of inequality spans the entire society. The ill-health and social problems that are associated with inequality are therefore also seen across entire societies, not just among the very poorest; by the same token, in the more equal societies the improved health and well-being benefits everyone, not just the very poorest.

And that means closing the gaps is good for all of us.

2. Economic growth is not the answer. For the wealthiest nations, increasing absolute income levels does nothing to improve the health of the population or to reduce social problems. Improvements will not be achieved by pursuing more economic growth. As Wilkinson and Pickett put it:

rich countries have got to the end of the really important contributions which economic growth can make to the quality of life … our future lies in improving the quality of the social environment in our societies. (p.265)

What is needed, quite simply, is more equality.

(Of course, among poorer developing nations, economic growth is important for improved health and wellbeing; however, once the per capita national income reaches around US$25,000, growth ceases to be a factor. The rules of the game change, and equality becomes the key factor in public health and social wellbeing.)

Further information

This work cuts right through the Gordian knot of many intractable policy debates. With supporters in the UK, Wilkinson and Pickett have set up The Equality Trust to make their findings more widely known. Let’s help spread the word!

PS (added 18/12/09)

The New Statesman magazine has named The Spirit Level as one of its Top 10 books of the decade, writing that “the book’s influence stretches across party lines and its findings are likely to shape political debate for many years to come.”

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