ジニ係数
The Gini coefficient is a relevant statistical tool when analyzing the idea of a wealth tax as a means of redistribution. The Gini coefficient ranges from zero to one, zero indicates perfect equality while one indicates perfect inequality. The Gini coefficient, however, can be used to measure both the distribution of wealth and the distribution of income. These are two very different concepts, and thus the unqualified use of the term can be confusing. For instance, when the Gini coefficient is used as measure of income distribution of a population, the figures for the U.S. come out very close to those of other countries. Federal Reserve Bank of St. Louis compared the Gini coefficient for income distribution of various countries and regions. With regard to the United States they found, "Income inequality in the United States is large, despite the U.S. having one of the highest levels of income per capita in our sample. Specifically, the Gini coefficient of the U.S. was 40.46 [in a 0-100 scale] in 2010, very close to the average Gini coefficient of African countries in our sample.". European nations, by comparison, generally have a Gini coefficient for income distribution that is between 0.24 and 0.36. Since 2010 the Gini coefficient for income distribution has risen in the United States and was 0.49 in 2018.