The effects of income inequality on health

Milbank Quarterly, 2004

Social Science & Medicine, 2006

Whether or not the scale of a society's income inequality is a determinant of population health is still regarded as a controversial issue. We decided to review the evidence and see if we could find a consistent interpretation of both the positive and negative findings. We identified 168 analyses in 155 papers reporting research findings on the association between income distribution and population health, and classified them according to how far their findings supported the hypothesis that greater income differences are associated with lower standards of population health. Analyses in which all adjusted associations between greater income equality and higher standards of population health were statistically significant and positive were classified as ''wholly supportive''; if none were significant and positive they were classified as ''unsupportive''; and if some but not all were significant and supportive they were classified as ''partially supportive''. Of those classified as either wholly supportive or unsupportive, a large majority (70 per cent) suggest that health is less good in societies where income differences are bigger. There were substantial differences in the proportion of supportive findings according to whether inequality was measured in large or small areas. We suggest that the studies of income inequality are more supportive in large areas because in that context income inequality serves as a measure of the scale of social stratification, or how hierarchical a society is. We suggest three explanations for the unsupportive findings reported by a minority of studies. First, many studies measured inequality in areas too small to reflect the scale of social class differences in a society; second, a number of studies controlled for factors which, rather than being genuine confounders, are likely either to mediate between class and health or to be other reflections of the scale of social stratification; and third, the international relationship was temporarily lost (in all but the youngest age groups) during the decade from the mid-1980s when income differences were widening particularly rapidly in a number of countries. We finish by discussing possible objections to our interpretation of the findings.

Milbank Quarterly, 2004

Healthier Societies, 2006

This chapter begins by reviewing research evidence on the relationship between income and health at the individual level, and examines studies that have followed individuals through time to demonstrate the direction of the relationship. This is a fundamental starting point since the individual relationship between income and health likely underlies any analysis examining the connection between income inequality and population health. The chapter introduces research regarding this connection, and then compares the relationship between income inequality and health in jurisdictions within Canada and the United States, finding significant differences. It concludes with a series of hypotheses about why health outcomes in Canada and the United States are so different.

Epidemiologic Reviews, 2004

Demography, 2009

We examine the effect of income inequality on individuals' self-rated health status in a pooled sample of 11 countries, using longitudinal data from the European Community Household Panel survey. Taking advantage of the longitudinal and cross-national nature of our data, and carefully modeling the self-reported health information, we avoid several of the pitfalls suffered by earlier studies on this topic. We calculate income inequality indices measured at two standard levels of geography (NUTS-0 and NUTS-1) and ¿ nd consistent evidence that income inequality is negatively related to self-rated health status in the European Union for both men and women, particularly when measured at national level. However, despite its statistical signi¿ cance, the magnitude of the impact of inequality on health is very small. umerous studies have reported an association between the level of income inequality in a population and aggregate health outcomes: average health among people living in highinequality areas appears to be lower than among people living in low-inequality areas. A statistically signi¿ cant relationship has been reported in studies using aggregate data both across countries (Rodgers 1979; Wilkinson 1992) and across regions within countries (Kawachi and Kennedy 1997; Lynch et al. 1998). This observation has lead researchers to argue that increasing income dispersion directly translates into poor health, thereby suggesting additional welfare gains from more progressive income redistribution policies. This argument is embodied in Wilkinson's (1996) controversial income inequality hypothesis (IIH), which posits that the primary determinant of differences in health performance among developed countries is the extent of differences in the disparity between the incomes of the rich and the poor within countries rather than differences in income levels. Authors have typically conjectured that inequality has an effect on health either because it is a source of psychosocial stress, which eventually leads to stress-related afÀ ictions, or because it fosters the development of environments hazardous to public health (Daly et al. 1998). However, providing a fully convincing theory characterizing the actual direct (or indirect) pathways by which inequality affects health remains a contentious issue (for recent reviews, see Deaton 2003; Leigh, Jencks, and Smeeding 2009; and Subramanian and Kawachi 2004). Subramanian and Kawachi (2004) identi¿ ed three potential pathways by which greater income inequality may translate into poorer health. First, according to a structural pathways argument, increased inequality leads to spatial concentrations (poverty, race, ethnic enclaves), and residential segregation is potentially detrimental to individual health (Wen, Browning, and Cagney 2003). Second, building on the argument that individual health is inÀ uenced by social relations, the social cohesion and collective social pathway suggests that inequality affects health by weakening social cohesion and holding back the formation of social capital bene¿ cial to health (Kawachi et al. 1997). Third, policy

SSRN Electronic Journal, 2000

Social science & medicine (1982), 2015

There is a very large literature examining income inequality in relation to health. Early reviews came to different interpretations of the evidence, though a large majority of studies reported that health tended to be worse in more unequal societies. More recent studies, not included in those reviews, provide substantial new evidence. Our purpose in this paper is to assess whether or not wider income differences play a causal role leading to worse health. We conducted a literature review within an epidemiological causal framework and inferred the likelihood of a causal relationship between income inequality and health (including violence) by considering the evidence as a whole. The body of evidence strongly suggests that income inequality affects population health and wellbeing. The major causal criteria of temporality, biological plausibility, consistency and lack of alternative explanations are well supported. Of the small minority of studies which find no association, most can be...

Social Science & Medicine, 1998

Social Science & Medicine, 2010

This paper uses a unique dataset-containing information collected in 2006 on individuals aged 40-79 in 21 countries throughout the world to examine whether individual income, relative income in a reference group, and income inequality are related to health status across middle/low and high-income countries. The dependent variable is self-assessed health (SAH), and as a robustness check, activities of daily living (ADL) are considered. The focus is particularly on assumptions regarding an individual's reference group and on how the estimated relationships depend on the level of economic development. Correcting for national differences in health reporting behavior, individual absolute income is found to be positively related to individual health. Furthermore, in the high-income sample, there is strong evidence that average income within a peerage group is negatively related to health, thus supporting the relative income hypothesis. In middle/low-income countries, it is instead average regional income that is negatively associated with health. Finally, there is evidence of a negative relationship between income inequality and individual health in high-income countries. Overall, the results suggest that there might be important differences in these relationships between high-income and middle/low-income countries.