At the Intersection of Health, Health Care and Policy Cite this article as: Michael Marmot The Influence Of Income On Health: Views Of An Epidemiologist Health Affairs, 21, no.2 (2002):31-46 doi: 10.1377/hlthaff.21.2.31

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The Influence Of Income On Health: Views Of An Epidemiologist Does money really matter? Or is it a marker for something else? by Michael Marmot
ABSTRACT: Income is related to health in three ways: through the gross national product of countries, the income of individuals, and the income inequalities among rich nations and among geographic areas. A central question is the degree to which these associations reflect a causal association. If so, redistribution of income would improve health. This paper discusses two ways in which income could be causally related to health: through a direct effect on the material conditions necessary for biological survival, and through an effect on social participation and opportunity to control life circumstances. The fewer goods and services are provided publicly by the community, the more important individual income is for health. Under present U.S. circumstances, a policy of counteracting growing income inequalities through the tax and benefit system and of public provision appears justified.

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oes money matter for health? If so, why? If it does matter, there are at least three ways in which it could be important: not having enough money, maldistribution of money, and spending it on the wrong things. It is also possible that health could matter for money, that the causal direction could be the other way around. Of course, money could only appear to matter. It may be that poor people have worse health not because they have insufficient money but for some other reason. Similarly, a society characterized by a high degree of income inequality could have poor average health for reasons other than the distribution of income. Or countries that spend more money on surgeons may have better health because they are democratic, not because of the surgery. In each of these cases, money appears to matter because it is a marker for something else. Michael Marmot is professor and head of the Department of Epidemiology and Public Health, and director of the International Centre for Health and Society, at University College London. He was a member of the Scientific Advisory Committee, which prepared the 1998 Independent Inquiry into Inequalities in Health, under the leadership of Sir Donald Acheson. In 2000 Marmot was awarded a knighthood “for services to epidemiology and understanding health inequalities.”

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In come & Health

The distinction between really mattering and appearing to matter is important. For example, if it really matters, a policy devoted to income redistribution could have health benefits. If it only appears to matter, such a policy, whatever other positive or negative features it might have, will not benefit health. This is important for policy, and I return to it after considering the evidence. In asking if money matters, two types of evidence are relevant: the relation of income to health between and within countries, and the relation of income inequality to health. I also deal with two related debates: the degree to which the apparent relation of income to health should be thought of as a question of poverty or inequality; and the role of material and psychosocial factors in generating inequalities in health. I note that there is evidence that health can affect income, but that it is not the major explanation of the link between income and health. This has been dealt with elsewhere.1 I confine my attention largely to the rich countries of the world, not because the problems of health inequalities are absent from poor countries, but because the policy questions are different—lack of sanitation, clean water, and adequate nutrition, for a start—although I suspect that some of the policy questions may not be so different. 32 INFLUENCE OF HEALTH

Aspects Of Poverty: Material Conditions And Social Participation We cannot discuss income without considering its lack: poverty. There has been a long debate as to the merits of describing poverty in absolute or relative terms.2 To understand why income may be important for health, it is worth distinguishing two aspects of low income, which for simplicity I label “poor material conditions” and “lack of social participation.” Let me illustrate with a simple thought experiment. Suppose there were a set of material conditions, such as clean water and good sanitation, adequate nutrition, and adequate housing and warmth, that were necessary for good health. Suppose, too, that these material conditions were correlated with income until a threshold was reached. Clean water is necessary for good health. Once water is safe, higher income does not make it safer. Below the threshold, the lower the income, the worse the health because of the link with material conditions. Above the threshold level, differences in material conditions no longer have any plausible connection with differences in pathology. For people above the threshold, there still could be substantial inequalities in health that are related to differing opportunities for social participation, for leading a fulfilling and satisfying life, and for control over one’s life. Depending on how society was organized, these opportunities could show a strong

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direct link with individual income. In this case, income would be causally linked to health, albeit not through material conditions. Alternatively, the link to income of opportunities for participation and control could be more tenuous, in which case, once the threshold was reached, the relation of income to health would be weaker. Other socioeconomic markers, more strongly related to participation and control, would show a stronger relation to health. One could argue that it mattered little which pathway was important, material conditions or participation. If there were a link between income and health, a policy of equalizing incomes would reduce health inequalities. But what if such a policy were politically unacceptable? Do we not need to understand why incomes might be related to ill health in order to have the possibility to interrupt the chain of causation from economic position to health? A second reason for making the distinction between material conditions and participation is that the latter constitutes an important part of what people report poverty is about in Britain and other European countries. Poverty includes not having a hobby or leisure activity, not having friends or family round for a snack, not taking children swimming, not having a family holiday. These are related to individual incomes to a greater or lesser extent depending on purchasing power and public provision. They are not “material,” in the sense that clean water and good sanitation are. A third reason for making the distinction is that one can envisage circumstances in which there is a threshold level above which material conditions no longer influence health, but degree of participation and control could show no such threshold. Inequalities in these could account for inequalities in health above a threshold of material provision. Conversely, people who are relatively poor could have good health if their social participation were high. With these distinctions in mind, it is helpful to develop a little historical perspective on the question of poverty and health.

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Poverty And Health In Perspective
I Infant mortality. Infant mortality traditionally has been viewed as the measure of health, more strictly ill health, that is most sensitive to poverty. Let us look at one historical exam...

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