What is the Gini ratio?
What is it? It is an index of income concentration, articulated by the Italian statistician Corrado Gini in 1912.
How is it defined? The Gini (or GINI) coefficient (or index or ratio) ranges from zero to one (or, as a percentage, from zero to 100). A measure of zero indicates perfect equality, i.e., all people have equal shares of income, whereas a measure of one indicates perfect inequality, i.e., a single person has all the income and the rest have none.
Caveats: Income is distinct from wealth. The Gini index can be the same for two Lorenz income-distribution curves of very different shape. It is sensitive to outliers. The U.S. Census Bureau usually reports using pre-tax numbers, whereas foreign reporting may use post-tax numbers including transfers (e.g., efforts to redistribute from rich to poor).
In Data Buffet: Gini indexes for the U.S. and portions thereof are published by the U.S. Census Bureau in the American Community Survey (concept code ACSGINIHHA), Current Population Survey (GINIHH and HHCPSYGINIA), and decennial census. For other countries, they appear in the African Development Indicators (WBKADILWQGINIUA) and World Development Indicators (WBKSIPOVGINIUA), both published by the World Bank.
[DISCONTINUED] Africa Development Indicators
Median Family Income - CPS
Selected Characteristics of Households by Total Money Income (HINC-01) - CPS ASEC
U.S. Decennial Census Data
World Development Indicators (WDI)