Income inequality measures fall into two categories: one-number summary statistics, such as the Gini index,

and information about the income distribution at various points, such as shares of income or percentile ratios.

One-number summary statistics measure the income distribution throughout the entire distribution. The Gini index ranges from zero (perfect equality) to one (one individual or household receives all the income and the others receive none). The concentration coefficient is a variant of the Gini index, with the only difference being that individuals are not ranked by the values of the income concept for which inequality is computed, but by their disposable income. Shares of income or percentile ratios provide a picture of inequality at specific points in the

income distribution, by comparing, for instance, the income of the 90

th percentile to that of the 10

th percentile