Volume 16, Number 2
There are many numbers that matter for a person’s health. On an individual basis, heart rate, blood pressure, BMI (body mass index) are commonly assessed. For an individual with diabetes, HbA1c is followed. With respect to social determinants of health, number of years of education, income, and zip code are numbers that are relevant for health.
The Gini coefficient is a number that falls into the category of social determinants of health, as it is an index of the statistical distribution of wealth in a designated population. It has become the most common number used for measuring income inequality, the width of the gap in wealth between the richest and poorest segments of a population. Therefore, the Gini coefficient is a metric by which income inequality is compared among countries, states, or counties. In the United States, the Gini coefficient has been rising. In 1978, the top 10% of the population earned 30 percent of income, whereas in 2014 the top 10% earned 50% of the income (Health Affairs, October 2018).
Higher income inequality has consistently been found to be related to poorer health in comparisons among counties, US states, and countries. With over 300 peer-reviewed studies of the relationship between income inequality and health, at least 94% of these studies reported a “significant association between greater inequality and worse health” (American Public Health Association, 2017). For example, a study published in 2016 in the Journal of the American College of Surgeons compared over 1,200 counties in the United States and found that as the Gini coefficient went up, so did health care use and expenditures. At the state level, higher income inequality is associated with higher rates of alcohol consumption, obesity, heart disease, and depression, among many other physical and mental health problems (The Social Science Journal, 2018). In 2019, a study published in the Journal of the American College of Cardiology examining data from 54 countries found that worse heart failure outcomes were associated with income inequality, to a degree similar to common prognostic indicators.
It is important to note that while persons with lower incomes are commonly found to have poorer health than those with higher incomes, the impact of income inequality does not simply affect the poor. Some studies find that the negative impact of a higher Gini coefficient is greater for the rich than the poor. While this isn’t fully understood, the most common theory is that the chronic stressors associated with income inequality in a community or society affect persons across the economic spectrum.
Also important to note is that health factors themselves can serve to increase the Gini coefficient in a population. Poor health impacts persons differentially on the income spectrum. The financial resources of wealthier individuals tend to be more diversified and therefore are less dependent on job income, whereas poorer individuals are more dependent on earnings from a job. Job loss because of health problems tends to have a more negative impact on the financial status of poorer individuals, which in turn conveys additional risk for further health problems.
The Gini coefficient for Ohio tends to rank near the middle of states (26th). Among the 37 OECD countries (Organization for Economic Cooperation and Development), only 5 countries have higher Gini coefficients than does the United States. This is considered one reason why the United States has relatively poor health outcomes, especially since the US spends more money on health care than does any other country.
Of course, the topic of income inequality is a political and economic matter. While an individual can largely control what one chooses to eat or whether one exercises, impacting income inequality is much less straightforward. Rather, an individual’s role in the Gini coefficient is one’s contribution to choices made by collectives of people, whether that be at the county, state, or national level.
Paul J. Hershberger, Ph.D.
… is a clinical health psychologist. He is Professor, Director of Research, and Director of the Division of Behavioral Health, Department of Family Medicine, Wright State University Boonshoft School of Medicine.
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