THE GINI COEFFICIENT
The Gini Coefficient is a summary measure that captures the deviation shown in the Lorenz curve. It is calculated as follows:
where xi and yi are the relative frequencies, rather than the cumulative frequencies, and k is the number of classes/groups.
The Gini Coefficient can be expressed graphically with the Lorenz curve, where: G = A/(A+B), where A is the area between the line of equality and the Lorenz curve, and B is the area under the Lorenz curve.