This JRF report by  Karen Rowlingson provides an independent review of the evidence about the impact of inequality, paying particular attention to the evidence and arguments put forward in ‘The Spirit Level’ by Richard Wilkinson and Kate Pickett (2009). The research examines:

• whether or not there is a link between income inequality and health and social problems
• who might be most affected by income inequality
• other possible impacts of income inequality, for example, on the economy.

It concludes that the evidence from a range of studies suggests that there is indeed a correlation between income inequality and health and social problems. There is less agreement about whether or not there is a causal relationship, but some rigorous studies provide evidence of such a relationship.  In studies which do show that income inequality causes health and social problems, the size of this effect looks small in statistical terms; however, since these studies involve whole populations, the numbers of lives involved are significant. Some research suggests that inequality is particularly harmful after it reaches a certain threshold. Britain was below this threshold in the 1960s, 1970s and early 1980s, but has settled well above that threshold since 1998–9.