Income Equality

Income Equality is based on the Gini coefficient, which measures income inequality as the difference between the observed cumulative income distribution in an area and a perfectly equal income distribution (Gini index description). The Gini coefficient ranges from 0 to 1, with larger values indicating greater income inequality. As a general rule, Gini scores < 0.2 represent perfect income equality while scores > 0.5 indicate severe income gaps, thus a score of 0.4 can serve as a warning level of income inequality (Teng et al. 2011).

How is it scored?

County-level Gini coefficient scores were converted to a 0–100 scale so that a Gini coefficient of < 0.2 was scored as 100%, coefficient scores from 0.2–0.4 were scored in the 40% to 99% range, and an coefficient score greater than 0.4 ranged from 0% to 40% (Table 1). 

Table 1. Equations used to convert Gini coefficient scores to report card score (0–100).

County-level scores were population-weighted and summed to calculate the watershed score. Watershed scores were weighted by their population size to calculate an overall score for southeast Michigan.

Data source: Data was downloaded at the county-level from the US Census Bureau (US Census Bureau) for 2020.