Wikipedia: Gini coefficient - "Wealthy countries such as Sweden can show a low Gini coefficient for disposable income of 0.31 thereby appearing equal, yet have very high Gini coefficient for wealth of 0.79 to 0.86 thereby suggesting an extremely unequal wealth distribution in its society."
The Gini coefficient measures the inequality among values of a frequency distribution (for example levels of income). A Gini coefficient of zero expresses perfect equality, where all values are the same (for example, where everyone has an exactly equal income).
Watch the growth of U.S. income inequality with this animated map
"The map was created by John Voorheis, a graduate student at the University of Oregon, and was passed along by Mark Thoma of Economist's View. More specifically, the map shows the change in Gini coefficients — a measure of income inequality — within states over time."