Journal of the American Medical Association (pg. 425), January 28, 2009

RELATIVE CHILD POVERTY, INCOME INEQUALITY, WEALTH, AND HEALTH

[Rachel's introduction: Exposure to relative poverty or having a low socioeconomic position in childhood has been associated with increased adult morbidity [sickness] and mortality [death] resulting from (among other causes): stomach, liver, and lung cancer; diabetes; coronary heart disease; stroke; respiratory diseases; nervous system conditions; diseases of the digestive system; alcoholic cirrhosis; unintentional injuries; and homicide.]

By Eric Emerson, Ph.D.

Abundant evidence now suggests that living in relative poverty and exposure to relative income inequality, especially in childhood, may have a detrimental influence on health and well-being during childhood and across the life course. This Commentary discusses the importance of relative poverty in childhood and the implications of income inequality for population health.

Child relative poverty (ie, children living in a household with relative income poverty) appears to be a potentially important indicator for children's health. Relative income poverty is commonly defined as having equivalized household income of less than 50% of the national median.[1] Equivalization is calculated by dividing household income by an indicator of household composition or need, for example, the square root of the number of individuals living in the household.[2] Child relative poverty is strongly related to overall income inequality as measured by the Gini coefficient, which reflects inequalities in the distribution of income and wealth for the population of a nation; a lower Gini coefficient suggests more equal income or wealth distribution, whereas a high Gini coefficient reflects more unequal distribution of income and wealth.[3] For instance, the United States has both the highest national wealth and the highest Gini coefficient.[3] Thus, in the United States, as with many of the world's richest countries, there is little or no association between national wealth and the levels of income inequality evident within those nations.

Given that relative poverty is defined in terms of deviation from country-specific median income, there is no a priori reason to expect an association between relative poverty and national wealth. Two factors appear to be particularly relevant to understanding the variation in relative poverty.[1,2] First, clear international differences in income inequality (and the consequent risk of exposure to relative poverty) result from levels of participation in and the operation of labor markets. Second, redistributive income policies (the combined effects of progressive direct taxation and provision of welfare benefits) play a key role in attenuating market-driven inequalities and thereby in determining rates of child relative poverty and income inequality experienced by the population.

For instance, a recent Organisation for Economic Co-operation and Development study reported that child relative poverty rates in 2000 calculated without taking into account any effects due to taxation and benefits were more than 25% in the United Kingdom, France, Australia, New Zealand, and the United States.[2] However, the effects of redistributive income policies varied markedly across these countries, reducing actual child relative poverty rates by more than 70% in France (from 28% to 7%) by more than 50% in Australia (from 27% to 15%), by more than 40% in the United Kingdom (from 29% to 16%) and New Zealand (from 29% to 15%), and by just 18% in the United States (from 27% to 22%).[2]

Relative child poverty appears to be associated with health and, in particular, the health of nations. For example, international or interstate variation in rates of income inequality or child relative poverty have been associated with higher rates of adverse health outcomes1,[4-11] including the following: poorer overall child well- being, infant mortality, low birth weight, not having polio immunizations, child mortality due to unintentional injuries, juvenile homicide, low educational attainment, dropping out of school, nonparticipation in higher education, aspiring to low-skilled work, poorer peer relations, having been bullied, teenage birth rate, physical inactivity, childhood obesity, not eating breakfast, feeling lonely, and mental health problems.[5] Moreover, across nations with wide ranges of per capita income and poverty levels, there appears to be an ecologic association between child relative poverty rates and mortality rates for children younger than 5 years (see Figure in the PDF). Similarly, exposure to relative poverty or having a low socioeconomic position in childhood has been associated with increased adult morbidity and mortality resulting from (among other causes): stomach, liver, and lung cancer; diabetes; coronary heart disease; stroke; respiratory diseases; nervous system conditions; diseases of the digestive system; alcoholic cirrhosis; unintentional injuries; and homicide.[9-10] See Figure in the PDF.

Relationship Between Relative Child Poverty and Under Age 5 Mortality in High-Income OECD Countries

Child relative poverty rates were extracted from data reported in the 2005 United Nations Children's Fund (UNICEF) report on child poverty in the world's rich countries.[12] Child relative poverty was defined as having equivalized household income (equivalized by dividing total household income by the square root of the number of individuals living in the household) of less than 50% of the national median.

Mortality rates of children younger than 5 years for the same period covered by the poverty estimates were extracted from data reported in the 2003 UNICEF report on the State of the World's Children.[13] Data are presented for all high-income Organisation for Economic and Co- operative Development (OECD) countries for which data were available in the 2 reports. Linear regression was used to estimate and plot the linear trend between relative child poverty and mortality rates of children younger than 5 years (r2 = 0.56; relative child poverty = -0.09 + 0.04 x mortality in children younger than 5 years).

It is therefore not surprising that increasing attention is being paid to reducing child relative poverty (or ameliorating the effects of child relative poverty) as a central component of attempts to improve the health of nations and reduce health inequalities between and within nations.[4,11] Indeed, there exists a sound evidence base regarding the determinants of child relative poverty and many examples of successful approaches to reducing child relative poverty.[4,12,14] Addressing these issues is not merely a matter for health professionals and health policy but centrally concerns the willingness of the electorate in democracies to tolerate the existence of inequality and its effects.

Author Information

Corresponding Author: Eric Emerson, PhD, Division of Health Research, Lancaster University, Lancaster, LA1 4YT, United Kingdom (eric.emerson@lancaster.ac.uk).

Author Affiliations: Division of Health Research, Lancaster University, Lancaster, England; and Faculty of Health Sciences, University of Sydney, Sydney, Australia.

References

[1] Graham H. Unequal Lives: Health and Socioeconomic Inequalities. Maidenhead, England: Open University Press; 2007.

[2] Whiteford P, Adema A. What Works Best in Reducing Child Poverty: A Benefit or Work Strategy? Paris, France: OECD; 2007. OECD Social, Employment and Migration Working Papers No. 51.

[3] United Nations Development Programme. Human Development Report 2007: Fighting Climate Change. Human Solidarity in a Divided World. New York, NY: United Nations Development Programme; 2007.

[4] World Health Organization. Closing the Gap in a Generation: Health Equity Through Action on the Social Determinants of Health: Final Report of the Commission on the Social Determinants of Health. Geneva, Switzerland: World Health Organization; 2008.

[5] Pickett KE, Wilkinson RG. Child wellbeing and income inequality in rich societies: ecological cross sectional study. BMJ. 2007;335(7629):1080-1086.

[6] Kuh D, Power C, Blane D, Bartley M. Socioeconomic pathways between childhood and adult health. In: Kuh D, Ben-Shlomo Y, eds. A Life Course Approach to Chronic Disease Epidemiology. 2nd ed. Oxford, England: Oxford University Press; 2004.

[7] Marmot M. Social determinants of health inequalities. Lancet. 2005;365(9464):1099-1104.

[8] Wilkinson RG. The Impact of Inequality. New York, NY: The New Press; 2005.

[9] Galobardes B, Lynch JW, Davey Smith G. Childhood socioeconomic circumstances and cause-specific mortality in adulthood: systematic review and interpretation. Epidemiol Rev. 2004;26:7-21.

[10] Galobardes B, Lynch JW, Davey Smith G. Is the association between childhood socioeconomic circumstances and cause-specific mortality established? update of a systematic review. J Epidemiol Community Health. 2008;62(5):387-390.

[11] Irwin LG, Siddiqi A, Hertzman C. Early Child Development: A Powerful Equalizer. Geneva, Switzerland: World Health Organization; 2007.

[12] UNICEF. Child Poverty in Rich Countries 2005. Florence, Italy: UNICEF Innocenti Research Centre; 2005.

[13] UNICEF. State of the World's Children 2003. New York, NY: UNICEF; 2002.

[14] UNICEF. Child Poverty in Perspective: An Overview of Child Well- being in Rich Countries. Florence, Italy: UNICEF Innocenti Research Centre; 2007.