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Income Distribution and Life Expectancy: A Critical Appraisal
Judge, Ken, 1995. British Medical Journal, 311:1282–1285. †
This paper refutes the claims made in previous papers by Richard Wilkinson that income
inequality is the key determinant of variations in average life expectancy at birth among developed
countries. Judge reviews the two of primary sources used by Wilkinson and discusses his own research based on
more recent data.
Wilkinson's first primary source is criticized for not exercising due caution for the
effect of differences in family sizes between countries. The data from the second primary source is
considered somewhat unreliable and certainly not appropriate for the analysis that Wilkinson carried out.
Judge's research is based on a study by Förster of income distribution in 13
countries of the Organization for Economic Co–operation and Development (OECD) and the report Inquiry
into Income and Wealth by Goodman and Webb. This data casts doubt on the general hypothesis that inequalities
in income distribution are closely associated with life expectancy.
Judge suggests that the strength of the relationship between income inequality and
average life expectancy has been exaggerated. He views it as a predominantly monocausal explanation of
international variation in life expectancy. In his opinion, variations are the product of many influences,
which probably interact over long periods of time. He proposes such factors may be dietary influences,
cultural factors and national perceptions of self–esteem.
However, Judge concedes that there are many other indicators of income distribution,
other than those used, which could be computed. Therefore it is possible that one or more may be found to be
associated with life expectancy. The Goodman and Webb report showed a substantial increase in inequality of
disposable income from about 1984, but this was not significant. It is mentioned that a lagged relationship
may exist which would take some time to manifest itself.
Judge does not deny that citizens of the poorest countries can expect to live for many
decades less than those of the richest nations. However, among developed countries, variations in the average
life expectancy are not so great, but there are differences which cannot easily be explained by reference to
economic prosperity. He does not challenge the view that inequalities in living standards are associated
with health differences within countries, as distinct from average levels between nations.
Judge recommends that future exploration of the relationship between income distribution
and life expectancy should use more sophisticated multivariate methods. He also suggests that future attempts
to investigate the income inequality hypothesis should specify a priori what measures of income distribution
might be expected to be associated with life expectancy and why.
The paper is followed by a commentary in the form of a reply from Richard G. Wilkinson.
Wilkinson highlights that his is not the only evidence of the association between
national mortality rates and income distribution. He proceeds to summarize additional evidence that exists
for developed countries, developing countries and a combination of both.
Wilkinson disagrees that income is a monocausal explanation, viewing it rather as a
determinant and indicator of a wide range of material factors, covering all aspects of the standard of living
and also having a crucial impact on psychosocial factors, e.g. sense of control, security, status. He
highlights that the association between income and mortality has been found to be independent of fertility,
maternal literacy and education in developing countries and of average incomes, absolute levels of poverty,
smoking, racial differences and various measures of the provision of medical services in developed
countries.
He suggests that a large impact may be on younger lives and that combining all ages in
life expectancy could mask this impact.
Judge's data on OECD countries was obtained from the Luxembourg Income Study. This data
was subsequently removed from the database as they had become so badly corrupted. Wilkinson also criticizes
Judge's analysis for confounding the secular improvement in life expectancy with the effects of income
distribution.
Wilkinson concludes that future research is likely to rely heavily on superior quality
and quantity of data and that measures of income distribution will emphasize the economies of scale in large
households, while considering the problem of low response rates in some income surveys.
† This study is based on 13 countries of the Organisation for Economic Development
and Co–operation.