Equality

Equality between Rich and Poor (economic inequality)
Economic inequality refers to inequality among individuals and groups within a society, but can also refer to inequality among countries. The issue of economic inequality is related to the ideas of equity: equality of outcome and equality of opportunity.

Inequality is most often measured using the Gini coefficient, a statistic used to demonstrate the dispersion of wealth in a group. The Gini coefficient (The Gini Index or the Gini ratio): it is the most commonly used measure for the purposes of comparison because it measures the inequality among values of a frequency distribution. The Gini coefficient of zero expresses perfect equality, where all values are the same. A Gini coefficient of one (100 on the percentile scale) expresses maximal inequality among values.

Sources:

http://blogs.longwood.edu/engl150sec1314/files/2012/10/1-gap-between-the-rich-and-the-poor.jpg https://www.boundless.com/sociology/textbooks/boundless-sociology-textbook/stratification-inequality-and-social-class-in-the-u-s-9/social-mobility-76/growing-gap-between-rich-and-poor-450-2081/ https://www.boundless.com/sociology/textbooks/boundless-sociology-textbook/stratification-inequality-and-social-class-in-the-u-s-9/social-mobility-76/growing-gap-between-rich-and-poor-450-2081