Greater equality and better healthBMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b4320 (Published 11 November 2009) Cite this as: BMJ 2009;339:b4320
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From the standpoint of the empirical social scientist, working in the
field of cross-national development research, Dr. Wilkinson’s hypotheses
about the causal trade-off between inequality and low health, manifesting
itself in various social indicators, such as life expectancy and infant
mortality, sound reasonable, but are methodologically and statistically
Dr. Jason Beckfield from the Department of Sociology at Chicago
University (2006), like myself a scientist from the empirical, macro-
quantitative current of social science, recently came to the conclusion
that, I quote:
“This study replicates previous work using a larger sample (692
observations from 115 countries over the 1947-1996 period), a wider range
of statistical controls, and fixed-effects models that address
heterogeneity bias. The relationship between health and inequality shrinks
when controls are included. In fixed-effects models that capture
unmeasured hetero- geneity, the association between income inequality and
health disappears. The null findings hold for two measures of income
inequality: the Gini coefficient and the share of income received by the
poorest quintile of the population. Analysis of a sample of wealthy
countries also fails to support the hypothesis”
Much of the research, published by Dr. Wilkinson over the past
decades, looks merely into the bi-variate correlations between inequality
and social performance at the level of OECD democracies. But currently,
global social science now has data about inequality from practically all
over the globe at its disposal.
So do Dr. Wilkinson’s hypotheses hold when we look, for example at a
global sample, which includes the low life expectancies, high infant
mortalities and devastating rates of alcoholism, combined with relatively
low (but rising) inequalities in several former communist countries after
the transformation? Is “equality” associated in a causal way with “good
health” or rather alcoholism? High taxes, low economic growth? These are
just provocative questions, to which quantitative social science has to
Limiting his research to relatively small samples is error number 1
in Dr. Wilkinson’s approach. Error number 2 is that Professor Wilkinson
overlooks the curve-linear trade-off between development levels and
inequality levels. This effect is known to economists and social
scientists ever since the path-breaking article by Professor Simon
Kuznets, Nobel laureate in economics, first published in 1995. A human
being’s intelligence does not depend on the size of the big toe, once we
control for the age factor.
Error number 3 consists in overlooking what colleague Joshua
Goldstein, back in 1985, called the “plateau curve of basic human needs”.
Like inequality, life expectancy depends on development levels, and the
trade-off is again in the shape of an inverted “U”.
I provide the readers of this journal with some of the cross-national
evidence which would be available today on the subject. Table 1 shows the
sometimes powerful effects at the level of the OECD countries, still
vindicating Wilkinson’s approach:
Table 1: Perason Bravais product moment correlations of the difference in incomes between the richest 20% and the poorest 20% (quintile share) in the OECD countries and in the world system
Source: our own calculations with the standard international data, downloadable from http://www.hichemkaroui.com/?p=1317; SPSS XV, Innsbruck University
Table 2 now shows the relationship between inequality and the life
quality variables, once we keep the curve-linear effects described by
Kuznets (1955) and Goldstein (1985) constant. What happens is that several
effects are reduced, and explain just around 10% of the variance of the
life quality variables at the level of the world system.
Table 2: partial correlations (keeping constant the nat. logarithm of GDP per capita at purchasing power parity rates and its square) of the difference in incomes between the richest 20% and the poorest 20% (quintile share) in the OECD countries and in the world system
I think a way forward in this debate would be a true dialogue between
medicine, public health and the social sciences. Neo-classical economists
like Barro, Durlauf with associates, and Sala-i-Martin, and world system
scholars, like Herkenrath and Bornschier, who stress the importance of the
globalization factor in blocking long-run socio-economic development, are
correct in showing that nowadays social science has to take a variety of
factors into account to explain the paths of socio-economic development
1. Barro R. J. and Sala-i-Martin X. (2003), ‘Economic Growth’.
Cambridge, MA: MIT Press, second edition.
2. Beckfield J. (2006), ‘Does Income Inequality Harm Health? New Cross-
National Evidence’ Journal of Health and Social Behavior, Vol. 45, No. 3
(Sep., 2004), pp. 231-248
3. Goldstein J. S. (1985), Basic Human Needs: The Plateau Curve. World
Development, 13(5), 595 - 609.
4. Durlauf St. N., Kourtellos A., Tan Ch. M. (2008); Are any Growth
Theories Robust? The Economic Journal, 118(1), 329–346.
5. Herkenrath M. and Bornschier V. (2003), “Transnational Corporations in
World Development – Still the Same Harmful Effects in an Increasingly
Globalized World Economy?” Journal of world-systems research, ix, 1,
winter 2003, 105–139, http://jwsr.ucr.edu, issn 1076–156x
6. Kuznets S. (1955), 'Economic Growth and Income Inequality' The American
Economic Review, 45, 1: 1 - 28.
7. Kuznets S. (1976), Modern Economic Growth: Rate, Structure and Spread.
New Haven, CT: Yale University Press.
8. Sala-I-Martin X.; Doppelhofer G. and Miller R. I. (2004), ‚Determinants
of Long-Term Growth: A Bayesian Averaging of Classical Estimates (BACE)
Approach.’ American Economic Review, Sep 2004, Vol. 94 Issue 4, p813-835.
9. Tausch A. and Prager F. (1993), ‘Towards a Socio-Liberal Theory of
World Development’. Basingstoke and New York: Macmillan/St. Martin's
10. Wilkinson R. G. (1992), ‘Income Distribution and Life Expectancy’ BMJ,
304, 6820, 165-168
11. Wilkinson R. G. and Picket K. E. (2006), ‘Title: Income inequality and
population health: A review and explanation of the evidence’, 62, 7, 1768-
All the variables, based on such sources as UNDP, are contained in:
Competing interests: No competing interests
Equality, health and other social ills
Pickett and Wilkinson BMJ 2009;339:1154-1155
This is a very remarkable hypothesis. If the underlying science is
true, it is a paradigm shifting thesis, like evolution or germ theory. In
essence Wilkinson and Pickett assert that they have evidence that many of
the ills of modern prosperous societies, from obesity and drug abuse
through teenage pregnancies to violence and bulging jails all have a
common cause; income inequality.
This is a ground breaking assertion because it renders large areas of
political discourse irrelevant. Almost every day on the Radio 4 Today
programme topics are discussed which are importantly affected by this
hypothesis. Cameron's broken society and Brown's suggestion of hostels for
teenage mothers both need the same solution, a more equal society. Indeed
the evidence is so powerful that it implies that unless we can achieve
more equal societies other action will not work, thus the redundancy of
much present political discussion.
I have known about Wilkinson's work on inequality and health for at
least 20 years but the thesis is now enlarged into other measures namely;
levels of trust, mental illness (including drug and alcohol abuse), life
expectancy and infant mortality, obesity, children's educational
performance, teenage births, homicides, imprisonment rates and social
Clearly, in unequal societies the poor suffer the most, but another
intriguing assertion, with evidence, is that there is a fine
stratification of disadvantage which permeates society to the very top.
This also has been known for many years in the narrower field of medicine
from Marmot's well known Whitehall study. This present book broadens the
canvas dramatically and shows that rich people in unequal societies are
less healthy and happy than the top layers of more equal countries. In the
19th century, cholera and typhoid came roaring out of the slums to affect
the middle classes and even Prince Albert, so once the germ theory was
understood, clean water and good sewage disposal became a benefit for all.
The poor benefited the most, because they died the most but everyone
benefited. The analogy today is that as criminality, anti-social behaviour
and dependency costs bubble up out of the poorest areas of cities,
everyone's life would be improved by more equality.
This is a rich country analysis. No-one doubts that the lives of
people in poor countries can only be improved by economic advance. There
is however a turning point (maybe $20000 per head per year) after which
further increases in wealth are not accompanied by improved social
statistics. The richest and most unequal country of all, the USA, passed
this turning point decades ago and further increases in its wealth have
only produced a violent society with a huge jail population where the
middle classes hide behind security locks in gated communities. The book
is a devastating critique of the failure of the US version of market
democracy which has dominated the world since 1945. There are other ways
to ride the capitalist beast. The Scandinavian countries and Japan, at the
egalitarian end of the spectrum, exemplify two very different ways. The
researchers are also able to show the effects of inequality between
different US states. This is extraordinary because it shows how powerful
the effect must be if it can be detected between states whose culture and
wealth vary so little. The differences between New York and New Hampshire
are far fewer than the differences between Portugal and Sweden yet the
parameter of inequality still predicts all its malign effects.
This book deserves the widest discussion. In a nod towards the illustrious
predecessor of 1859 I think it could be subtitled “Origin of Stresses” by
means of unnatural inequality. The authors also speculate in a very
interesting way at the end of the book on the biological plausibility of
human beings functioning better in more equal societies.
This book is nothing less than the scientific underpinning of centre
left politics. Therein lies its weakness because the conclusions have been
asserted by liberal lefties for more than a century, and this could be
thoughtlessly dismissed as more of the same. But it isn't. The important
thing is that here is EVIDENCE. Once you have evidence that swallows
migrate to Africa in the winter, you no longer have to speculate, as
Doctor Johnson did, about them hibernating at the bottom of lakes. The old
discourse is dead. Doubters may find it hard to accept that the only ASBO
we need is more equality. It may seem as improbable to them as a tiny bird
flying to Africa, it just happens to be true.
Seth Jenkinson Nov 09
PS a powerful characteristic of scientific truth is that it is true
even before it is known or accepted. eg Cigarettes caused lung cancer long
before it was known that they did. If inequality causes social ills
because of the nature of human beings, it remains true, even if we never
act upon the truth.
Competing interests: No competing interests
As pointed out by Professors Pickett and Wilkinson, and illustrated
in the references cited and analysed, recent proposed explanations for the
link between inequality and health fall into two categories:
"compositional" and "contextual". Compositional explanations focus on
demographics - unequal societies have worse health simply because they
have more poor people. Contextual explanations posit that negative health
outcomes arise from divisive and socially corrosive psychosocial aspects
of inequality. Stress and behaviour originating from negative deficits in
social status, friendship, social capital, and sense of control make
contextual explanations at least as plausible as demographic effects such
as lack of economic access to healthcare in a large portion of a
There are several indirect contributing effects of inequality to
negative health, including the role of poverty in maintaining resevoirs of
infection, and increased negative impacts from crime on health (both
direct by violence and indirect by stress factors). Another indirect
effect is the association between development associated with wealth as
conventionally measured by economic outputs and increased concentration of
disease causing pollution in the environment. None of these indirect
effects necessarily correlate directly with inequality, as opposed to
increasing development and urbanization.
But a potential significant contributor has been overlooked in recent
analyses of the relation between inequality and population health, namely
the negative impacts of wealth itself. Increased wealth tends to be
associated with increased access to remedial and crisis interventional
healthcare, but not necessarily with good preventive care and practices.
Wealthier lifestyles are associated with less exercise, overconsumption,
and other negative environmental and behavioural risks, making excessive
wealth itself a plausible negative factor for health outcomes and health
In the wealthiest economies, inequal distributions of incomes is
associated with differential quality of diet and exercise at the two
extremes, and a generally negative impact on quality of diet, exercise,
and environmental factors in the middle. The result is a very complex set
of influences which requires much careful study and analysis for any
However, in any analysis, the negative influences of excessive
leisure and consumption associated with increased wealth, and found
particularly in societies with large wealth disparities, which tend to
value conspicuous consumption, need to be considered along with the health
benefits accruing to wealthier populations.
Competing interests: No competing interests