Educational Research - the Ethics and Aesthetics of Statistics

13 A Bubble for the Spirit Level: Metricophilia, Rhetoric and Philosophy 197
the nineteenth century and the establishment of the connection between smoking
and lung cancer in the twentieth. There are well-known criticisms of epidemiology,
such as that methodological errors tend to result in ‘false positives’, that epidemiologists
are naïve or complacent about methodology, and that they do too little to
counter over-interpretation of epidemiological data by the media and the public
(Feinstein, 1989). There is also a line of thought that, as illustrated by the quotation
from Ness and Rothenberg prefixing this chapter, epidemiologists frequently
overstate the credentials of their discipline and offer in their place a distinctive form
of rhetoric.
In what follows I attempt to analyse the claims of The Spirit Level: Why More
Equal Societies Almost Always Do Better (Wilkinson & Pickett, 2009). I focus on
this book for several reasons. First, its emphasis on problems that can be remediated
in the social world, as opposed to in people’s heads by way of CBT or
other therapies, is on principle very welcome. Second, however, it seems to have
the capacity to defeat the critical faculties of many reviewers (for example ‘a bank
of evidence against inequality that is impossible to deny’, ‘its unarguable battery of
evidence’: both from the Guardian, 14 March 2009, Review p. 6). Third, it leaves
unsolved crucial questions about causality: about just how inequality ‘gets under
the skin’ to bring about the social and other effects that Wilkinson and Pickett identify.
To ask questions about causality is to search for the bubble of this chapter’s
title.
Wilkinson and Pickett started with the question why health within any population
typically deteriorates the further down the socio-economic scale you go. The
differences are at first sight puzzling since they cannot be explained in terms of gross
national product (GNP) or spending on health care. Some countries that spend heavily
on health care (such as Norway) do very well in terms of physical health and life
expectancy, while others that also invest heavily in health care (such as Switzerland)
do significantly worse. Crucially, it is not only the poor whose health suffers. In
unequal countries the health of the rich, as well as their levels of educational attainment
and all the other variables investigated, suffers too. The explanation given in
The Spirit Level focuses on inequality: both poor and rich suffer, in unequal (and
developed, broadly better-off) societies, from a range of problems more than people
in equal ones. The problems include drug and alcohol abuse, mental illness, lower
levels of educational performance, obesity, violence and murder. More people are
sent to prison; infant mortality levels are higher; people are less inclined to trust
their fellow citizens; there is less concern, as reflected in government spending, for
the developing world.
The writers’ method is to plot variables against levels of inequality in developed
nations, thus presenting evidence in the form of scatter diagrams (sometimes called
‘scattergrams’ or ‘scatterplots’). They then draw a computer-generated regression
line through the co-ordinates, which always inclines in a way that reveals the guilty
hand of inequality. This they describe as a ‘best-fit line’, which they only include ‘if
the relationship would be very unlikely to occur by chance’ (p. xv). There are nearly
40 such scatter diagrams (as well as numerous other graphs and charts). I include
several here to illustrate the approach. 5