This indicator responds to growing attention, nationally and globally, to income inequality. High levels of inequality are correlated with, among other things, life expectancy, infant mortality, crime, and social instability (source: U.S. Census).
How is it measured?
A standard measure of income inequality is the Gini Coefficient. Perfectly distributed income, with say 50% of the population having 50% of the income, has a Gini Coefficient of 0. The higher the Gini Coefficient (with a ceiling of 1), the higher the level of inequality. The U.S. Census five-year American Community Survey contains GINI Coefficient data at the county level. The data of the 197 counties that intersect the Chesapeake Bay watershed boundary are scored based on their Gini Coefficient, aggregated into regions, and then weighted by population. Data are from the U.S. Census Bureau (https://data.census.gov/).
Threshold levels
Scoring is based on different thresholds for the Gini Coefficient. A Gini Coefficient (x) less than 0.2 scores 100; from 0.2–0.3 scores between 80–99 based on the equation -200x +140; from >0.3–0.4 scores between 40–79 based on the equation -400x +200; and greater than 0.4 scores between 0–39 based on the equation -400x +200.