Wilkinson & Pickett, (W&P) state that society as a whole would be healthier, more successful and happier if the gap between rich and poor were narrowed. The “Spirit Level Book”, written by them in 2010, is one of the most influential books on social policy to date and argues that inequality affects not just those at the bottom of the ladder, but everyone at all levels. Rich countries perform better when social indicators are more equitable across society. This essay will evaluate the validity of Wilkinson & Pickett's conclusions by comparing the work of authors who make similar arguments with the work of authors who disagree with them. A comparison of these different approaches, with a critical look at what and how inequality is measured, reveals that there is no definitive answer to the problems raised by Wilkinson and Pickett, although many of their claims are valid. Supporting arguments/authorsWilkinson and Pickett draw on a wide range of elements such as health and wealth, income, mental well-being and homicide to support their argument. They measure health and happiness in relation to people's income and find that in every society rich people tend on average to be happier and healthier than poorer people in the same societies. Furthermore, Wilkinson and Pickett (2010) argue that health and social problems are worse in more unequal societies. Due to inequality, poverty, social exclusion of underclasses and their dependence on welfare, life expectancy is lower, mental illness and drug use are high, and educational success and social mobility are limited . Data on US society also finds a correlation between lower mortality rates and higher incomes, a central focus of the paper......ice, Cambridge: Policy Press.Deaton, A. (2003 ). “Health, inequality and economic development”. Journal of economic literature. 41(1), 113-158.Gadrey, J. and Catrice, F,J. (2006). The new indicators of well-being and development. New York::Palgrave Macmillan.McKay, S. (2010). Where do we stand on inequality? Reflections on recent research and its implications. Journal of Poverty and Social Justice. (18), 19-33. Rowlingson, K. (2011). Does inequality cause health and social problems? Birmingham: Joseph Rowntree Foundation. Snowdon, J, C. (2010). The spiritual level illusion: Fact-checking the left's new theory of everything. London: Little Dice.Stiglitz, JE Sen, A. and Fitoussi, J,P. (2010). Measuring our lives badly. New York: The New Press. Wilkinson, R., & Pickett, K. (2010). The Level: Why Equality is Better for Everyone. London: Penguin.