Income Gini-Index

Definition

The Gini-Index is a summary measure of income inequality in a country. The Gini coefficient summarizes the dispersion of income across the entire income distribution. The coefficient ranges from 0, meaning perfect equality (everyone has the same income), to 1, meaning perfect inequality (one recipient receives all the income).

Context/Impact on Health

The Gini-Index helps to shed light on how income and wealth are unequally distributed across the US population. In 2022, the Gini in the U.S. was 0.488, a decrease of 1.2% from 2021. This was the first year the Gini had decreased in the country since 2007 and is attributed to median household income declines at the middle- and top-income brackets. Despite this drop in the Gini, income inequality has grown substantially in recent decades. Since 1993, the Gini coefficient for the US has increased 7.6 percent. It is also estimated that the top 10 percent of earners receive around half of all income in the US.

Income is associated with morbidity and mortality through various clinical, social, and environmental mechanisms, and income-related health disparities have been growing over time. The US has some of the largest income-based health disparities in the world. Studies have shown that economic inequality is linked to disparities in life expectancy, with those at the top having longer life expectancies. Furthermore, low-income adults are five times as likely as those with incomes over 400 percent of the poverty line to report being in poor health. Low-income Americans also experience higher rates of heart disease, diabetes, strokes, and other chronic conditions compared to high-income Americans. These poor health outcomes are also linked to the built environment. For instance, low-income neighborhoods have a higher density of tobacco retailers and fast-food restaurants, and less access to fresh foods and environments conducive for physical activity. These environmental factors lead to higher rates of obesity and chronic diseases. Economic disparities also have intergenerational consequences, and poor health outcomes can contribute to lower incomes, creating a vicious cycle.

Data Collection Methodology

The American Community Survey (ACS) is a nationwide survey that collects information on the demographic, social, economic, and housing characteristics of the US population. The ACS is an ongoing survey sent to 3.5 million addresses each year. The ACS provides estimates of income inequality at the local, county, or state level, providing data estimates for all of the following: all 50 states, the District of Columbia, Puerto Rico, every congressional district, and all counties, census tracts, and zip codes. The Gini is based on the difference between the Lorenz curve (observed cumulative income distribution) and the notion of an equal income distribution.

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