20% Upper limit, Median income and 80% lower limit: cut off points for household income percentiles. 20% of households earn less than the 20% upper limit, the median income splits all households in half, 50% earn less and 50% earns more, and the 20% highest earning households earn more than the 80% lower limit. These are not direct measures of income inequality within each county, but wide gaps between the cut off points are and they also measures income inequality between counties.
Share bottom 20%, top 20% and top 5%: These are the shares of the total household income in each county that goes to the households with the lowest 20% of incomes, the highest 20% incomes and the highest 5% of incomes.
Ratio 80/20: This reflects the gap between the lowest and highest quintiles. It is calculated by dividing the 80% lower limit with the 20% upper limit.
Gini: The Gini Index is one of the most often used summary measures of inequality. It summarizes the dispersion of income across the entire income distribution