Will Wilkinson links to a milder example of this in a review by Claude S. Fisher in the July/August Boston Review. First, here's how Fisher summarizes their argument regarding the bad effects of inequality:
Inequality, they explain, makes people focus on status and their relative positions on the prestige ladder. Such obsessions, in turn, create anxiety, distrust, and social isolation, which raise people’s level of physiological stress. Finally, stress, as we all now know, exacts high costs. It weakens the immune system, for example, and drives people to poor coping behavior such as overeating and lashing out at others.This is apparently supported by lots of graphs and stats comparing countries, regardless of cultural or historical context, and, for the US, comparing states. But here's how Fisher gently mocks what looks like an inherent absurdity of this sort of envy-thy-neighbor explanation of social ills:
Instead [of the massive health-care bill], the president would make us all happier, healthier, and longer-lived, their logic suggests, if he could get the richest, say, 5 percent of Americans to leave the country.Or, as he says later, we could just censor the media -- in a good cause! -- to prevent the conspicuous displays of wealth that apparently generate all these harmful feelings.
Natalie Evans, of the Guardian, also has a column on the issue, that links to a lengthy report put out by Peter Saunders, called "Beware False Prophets" (PDF), with a much more detailed critique, including lots of graphs and stats as well. Its last section is entitled "Propaganda masquerading as science" (a familiar-enough theme these days in so-called social science generally). (To be fair, here's the authors' rebuttal to Saunders, and here's a rebuttal of the rebuttal. The last is interesting as coming from a "Kurdish-Swedish" perspective, on the Super-Economy blog of Tino Sanandaji.)
And then Ed West, in the Telegraph, piles on, linking to a whole book devoted to shredding the The Spirit Level -- Christopher Snowdon's The Spirit Level Delusion, subtitled "Fact Checking the Left's New Theory of Everything". For a demonstration of how easy it is to reverse correlations by just picking a different, in fact more complete, selection of populations and variables, see the "Graphs and sources" post on his supporting blog.
So. It certainly looks as though The Spirit Level is just another sad entry in the list of political abuses of science. Never mind the correlation/causation distinction, it doesn't even seem to get very far establishing correlation without cherry-picking data, and of course ignoring culture and history, not to mention an enormous number of other factors like race, ethnic make-up, income, institutions, social mobility, etc., etc.
But, before throwing it away altogether, it's worth asking: what if, despite everything, it were true? Would it make the case that the state should intervene in order to establish more equality? (Note that its case is that more equality is always better.) What of other, more important values, aside from the ones being measured -- values like aspiration, enterprise, justice, or freedom? Since we're dealing in hypotheticals now anyway, suppose that a similar study had been made regarding freedom itself, and found that societies with less freedom had better "social outcomes" on a variety of measures than those with more. Would it follow that the state should decrease freedom in order to make us happier? Would we, should we, in such a case aim for a kind of totalitarianism, say, on the grounds that slaves generally live longer? I don't think so myself, and I can only hope that others would agree.