The Gini coefficient is a commonly-used measure of income inequality that condenses the entire income distribution for a country into a single number between 0 and 1: the higher the number, the greater the degree of income inequality.
The Gini coefficient ranges from zero, when everyone has the same income, to 1, when a single individual receives all the income. A Gini coefficient above 0.4 is often seen as an important point. Inequality above this level is frequently associated with political instability and growing social tensions.