The scientific method is the idea that we’ve got to check out theories against that reality outside the window. Facts which break our theory truly break it – if it doesn’t stand up to checking against the universe then the universe wins.
At which point we can test The Spirit Level. This is the idea that inequality creates a number of problems for the society in which it exists. That’s a convenient theory, certainly. For there are those who would insist that inequality is in and of itself inherently evil and they’d just love to find some things it causes which are themselves generally held to be bad. The problem is that this theory doesn’t seem to hold up in that examination against that universe, the reality outside the window.
As Chris Snowdon points out:
The Spirit Level turned ten this month. A minor publishing sensation when it was published in March 2009, it used a series of scatter plots to make the case that income inequality is a major driver of a range of health and social problems. The authors, Richard Wilkinson and Kate Pickett, argue that these problems are directly linked to the rate of inequality and will rise or fall as inequality rises and falls. I argued in The Spirit Level Delusion (2010) that most of Wilkinson and Pickett’s statistical correlations were the result of selection bias in the countries, criteria and datasets used by the authors. They looked at the 50 richest countries in the world (on the basis that these societies were wealthy enough to not benefit from further growth whereas outcomes in poorer countries would be confounded by the effect of GDP). However, they only used 23 of these countries – often fewer – in their analysis. The poorest of them was Portugal but several countries with a higher GDP than Portugal were excluded for no good reason. When I added these countries, many of the associations with inequality disappeared
This bit we all know of course. But what happens when you take the same places but with data from a further decade? If the associations between inequality and doom are strong then they’ll shine through that extra data. If there was, how to put this, a certain amount of selection leading to the earlier associations then we’ll see that too.
What is it that we do see?
In summary, most of the biggest claims made by Wilkinson and Pickett in The Spirit Level look even weaker today than they did when the book was published. Only one of the six associations stand up under W & P’s own methodology and none of them stand up when the full range of countries is analysed. In the case of life expectancy – the very flagship of The Spirit Level – the statistical association is the opposite of what the hypothesis predicts. If The Spirit Level hypothesis were correct, it would produce robust and consistent results over time as the underlying data changes. Instead, it seems to be extremely fragile, only working when a very specific set of statistics are applied to a carefully selected list of countries.
Ah, yes, the original thesis was colei*, wasn’t it? Not that it will stop ideologues but given that inequality causes everything fails that meeting with reality the rest of us can and should ignore them.