Positive reviews In a review for
Nature, Michael Sargent said that "In their new book, epidemiologists Richard Wilkinson and Kate Pickett extend this idea" (of the harm caused by status differences) "with a far-reaching analysis of the social consequences of income inequality. Using statistics from reputable independent sources, they compare indices of health and social development in 23 of the world's richest nations and in the individual US states. Their striking conclusion is that the societies that do best for their citizens are those with the narrowest income differentials—such as Japan and the Nordic countries and the US state of New Hampshire. The most unequal—the United States as a whole, the United Kingdom and Portugal—do worst." In the
London Review of Books University of Cambridge lecturer
David Runciman said that the book fudged the issue of its subtitle thesis of its UK first edition, and asked whether it is that "in more equal societies almost everyone does better, or is it simply that everyone does better on average?" Later in the review he stated that, "More equality is a good thing and it’s an idea that’s worth defending." Richard Wilkinson responded to the review in a letter, claiming that "while pointing out that we do not have evidence on the fraction of one percent who are very rich, we show that people at all other levels of the social hierarchy do better in more equal societies".
Boyd Tonkin, writing in
The Independent, described it as "an intellectual flagship of post-crisis compassion, this reader-friendly fusion of number-crunching and moral uplift has helped steer a debate about the route to a kinder, fairer nation.
Will Hutton in
The Observer described it as "A remarkable new book ...the implications are profound."
Roy Hattersley in the
New Statesman called it "a crucial contribution to the ideological argument", and the
New Statesman listed it as one of their top ten books of the decade.
Critical response John Kay wrote in the
Financial Times that the book "is a powerful counter to any simple equation of social progress and the advance of GDP", but he warned that the causal relationships are complex, and said that other studies, such as the
World Values Survey, could also explain high performance of societies such as Sweden and Japan. He said that "the evidence presented in the book is mostly a series of scatter diagrams, with a regression line drawn through them. No data is provided on the estimated equations, or on relevant statistical tests". The significance tests and correlation coefficients were included in the November 2010 revised paperback edition of the book, and also appear on the Equality Trust website, where source data is also available and there is an explanation for the omission that "the book's intended readership was not confined to those with statistical training". Richard Reeves in
The Guardian called the book "a thorough-going attempt to demonstrate scientifically the benefits of a smaller gap between rich and poor", but said there were problems with the book's approach. "Drawing a line through a series of data points signals nothing concrete about statistical significance ... since they do not provide any statistical analyses, this can't be verified." He later noted that, "
The Spirit Level is strongest on Wilkinson's home turf: health. The links between average health outcomes and income inequality do appear strong, and disturbing".
The Guardian ranked
The Spirit Level #79 in its list of 100 Best Books of the 21st Century. In the
European Sociological Review, sociologist
John Goldthorpe argued that the book relied too heavily on
income inequality over other forms of inequality (including broader
economic inequality), and demonstrated a one-dimensional understanding of
social stratification, with
social class being in effect treated as merely a marker for income. He concluded that much more research was needed to support either the Wilkinson and Pickett "account of the psychosocial generation of the contextual effects of inequality on health or the rival neo-materialist account".
Charles Moore in
The Daily Telegraph declared it to be "more a socialist tract than an objective analysis of poverty".
Gerry Hassan in
The Scotsman maintained against Wilkinson and Pickett's claim that "more equal societies almost always do better" that it "is not possible to make the claim that everyone gains from greater equality", and suggests one of the book's "central weaknesses" is the "absence of the importance of politics.... They let neo-liberalism and free market fundamentalism off the hook".
Re-analyses and alleged failures to replicate In a 2017 essay, later published in his book
Hanging on to the Edges,
Daniel Nettle questioned whether Wilkinson and Pickett's psycho-social account of the effects of inequality was the main factor explaining the link between inequality and the various observed negative outcomes. With the use of some of his own simulations, he argues that if we assume there are
diminishing returns to income, the correlational patterns observed in
The Spirit Level are to be expected. He concludes that both the psycho-social effects described in
The Spirit Level and the impact of diminishing returns to income likely both contribute to explaining the observed correlations, and questions why Wilkinson and Pickett neglect to mention the latter explanation in their book. In 2010, Tino Sanandaji and others wrote an article for the
Wall Street Journal in which they said, "when we attempted to duplicate their findings with data from the U.N. and the Organisation for Economic Co-operation and Development (
OECD), we found no such correlation". Pickett and Wilkinson addressed the
Wall Street Journal article in a letter to the
Journal In their response to the Wall Street Journal they said ,"...we use income inequality data from the United Nations, rather than the OECD, because the OECD data were not intended primarily for cross-national comparisons. However, even if we test our results using the OECD measures we find 28 of 29 relationships are still significant".' Wilkinson and Pickett published a response defending each of the claims in the book and accusing Saunders in turn of flawed methodology. Christopher Snowdon, an independent researcher and adjunct scholar at the
Democracy Institute, published a book largely devoted to a critique of
The Spirit Level, entitled, ''The Spirit Level Delusion: Fact-checking the Left's New Theory of Everything''. One of its central claims is that the authors have cherry-picked throughout. Snowdon suggests that Wilkinson excludes certain countries from his data without justification, such as South Korea and the Czech Republic. The book includes homicide, but excludes suicide. Prison population is included, but not the crime rate or crime survey data. Government foreign aid is included, but (private) charitable giving is not. Datasets are selected or rejected to support the thesis of the authors. Likely cultural confounding factors are not taken into account. Regression lines are drawn which are dependent on a very small number of outlying countries, but this is not explained in the text. Correlation is confused with causation throughout. It also argues that Wilkinson and Pickett falsely claim the existence of a scientific consensus when much of the literature disagrees with their findings. Snowdon's book also asserts that some of Wilkinson's previous publications have been criticized on the basis that "the strength of the association...seems quite sensitive to which countries are included". Finally, in a reductio ad absurdum, the methods of TSL are used to show that the suicide rate is linked to the recycling rate. Wilkinson and Pickett released a response to questions from Snowdon and responded to similar criticisms in the
Wall Street Journal. Snowdon has in turn responded to their response on his blog. In response to criticism of the book, Wilkinson and Pickett posted a note on the Equality Trust website which stated: "Almost all of the research presented and synthesised in
The Spirit Level had previously been
peer-reviewed, and is fully referenced therein. In order to distinguish between well founded criticism and unsubstantiated claims made for political purposes, all future debate should take place in peer-reviewed publications." ==Impact==