Countries With The Biggest Gaps Between Rich and Poor By Bruce Einhorn October The U.N. Development Program recently came out with a report looking, among other things, at income inequality worldwide. The UNDP ranked countries and regions based on a number of factors, including their Gini coefficient, named for Italian statistician Corrado Gini. We have listed the world's most advanced economies based on their Gini score, with zero marking absolute equality and 100 absolute inequality. Scandinavian countries, Japan, and the Czech Republic have the least amount of inequality. The U.S. is among the most unequal, but it's not No. 1. To see which economy is, read on.