Socioeconomic Effects on Healthcare - What Is the Gradient?

"One of the central tenets of sociology is that social stratification results in the unequal distribution of desirable resources and rewards in society. In Keeping with this expectation, some of the earliest mortality records indicate the existence of a strong inverse association between socioeconomic status (SES) and mortality: persons of high social status lived longer than their less favored counterparts." (Williams 1990)

Poorer people die younger and are sicker than richer people; indeed, mortality and morbidity rates are inversely related to many correlates of socioeconomic status such as income, wealth, education, or social class. That economic deprivation is strongly related to ill health was perhaps first scientifically documented by René Villermé, who compared mortality rates and poverty across the arrondissements of Paris in the 1820s, although references to the relationship can be found in ancient Greek and Chinese texts. A gradient of health with social class (defined through occupation) has been documented in the United Kingdom since the first census in 1851. In the United States, the landmark study by Evelyn Kitagawa and Philip Hauser merged census and death records to document the relationship between mortality on the one hand and education, income, occupation, race, and place of residence on the other. The gradient persists in recent data. The National Longitudinal Mortality Study (NLMS) merged data from death records with responses from household surveys around 1980. People whose reported family incomes in 1980 were less than $5,000 in 1980 prices are estimated to have a life expectancy around 25 percent lower than those whose family incomes were above $50,000.(Rogot, et al, 1993)

What Is The Gradient?

The relationship between health and income is referred to as a "gradient" to emphasize the gradual relationship between the two; health improves with income throughout the income distribution, and poverty has more than a "threshold" effect on health. In the NLMS data the proportional relationship between income and mortality is the same at all income levels, which implies that the absolute reduction in mortality for each dollar of income is much larger at the bottom of the income distribution than at the top. The gradient is often assessed in terms of other variables; mortality declines with wealth, with rank, and with social status.

Addressing health inequalities.

Many people find it unjust that people should not only be unequal in the amount of goods and services they receive but also in the length and quality of their lives. They believe that addressing these income-related inequalities in health is an urgent task of health policy. The current British government sees the reduction of health inequalities as its primary health-related goal. Other commentators go further and see the economic and social structure of society--especially low income, income inequality, discrimination, and social exclusion--as the ultimate determinants, the "causes of causes," of disease and death. From this perspective, a thoroughgoing redistribution of income and wealth is the key to improving population health. Focusing on "downstream" causes such as the control of health-related behavior or health delivery systems is likely to be futile if the "upstream" causes in the underlying socioeconomic structure remain unreformed. Britain's Acheson report on health inequalities, commissioned by the first Blair government, is the leading example of a set of redistributive policy prescriptions for addressing health inequalities through primarily "upstream" policies. It subsequently formed the basis for a set of government proposals, including general income-support policies such as family and child tax credits, and increases in the minimum wage, which are justified on health grounds. (Mitchell, Shaw, Dorling 2000)

In this paper I review information on the gradient, as well as its theoretical interpretations, and ask whether it makes sense to design policy to address health inequalities. I try to determine whether redistributing income will improve population health, something that is frequently taken as obvious in the public health literature. In the final section, which discusses policy prescriptions, I argue that the evidence on the gradient strengthens the case for redistribution toward the poor. When low income and poor health go together, the poor are doubly deprived and thus have a greater claim on our attention than is warranted from their incomes alone. But I also argue that the reduction of the gradient, or of health inequalities more generally, is an inappropriate target for health policy.

What Causes The Gradient If Not Income?

Policy cannot be intelligently conducted without an understanding of mechanisms; correlations are not enough. Income might cause health, health might cause income, or both might be correlated with other factors; indeed, all three possibilities might be operating simultaneously. The relative importance of each story is almost certainly different at different times, for different causes of illness, and at different points in life. Unfortunately, there is no general agreement about causes. I will begin with a brief discussion of the most important mechanisms other than a direct causal effect of income on health: two-way causality between health and income, differential access to health-care, and health-related behavior. The argument here is that the three non-income stories, although important, do not provide a complete explanation of the gradient.

Effects of health on income.

Part of the gradient comes from the effects of health on income. The main mechanism works through the ability to work and its effects on earnings; the effect of health on wealth through out-of-pocket costs of medical care is important for some people but is of relatively small importance overall. If the effect of health on earnings were the major part of the story, the appropriate policy would be to address health directly using health-specific interventions. In addition, when calculating the returns to such interventions, we should also allow for the additional benefits on productivity. It is unfortunate and divisive that much of the public health literature on the gradient takes the position that the effects of health on socioeconomic status--known in this literature as reverse causality, "selection," or "drift"--are negligible. Yet economists and others have documented the effects of health on earnings in many contexts, perhaps most notably as a proximate cause of retirement. Indeed, the relationship between income and health is much muted among retirees, among whom