With the ACS, income inequity can now been seen longitudinally. The main measure of income inequality available through the census is the use of the Gini Index. The Gini Index is a summary measure of income inequality. As an index, it only has a value of between 0 and 1. A value of "0" would mean that every household had the same exact income; a value of "1" would mean that income was concentrated solely in a single household.
The index does NOT speak about the absolute levels of income - in other words, it doesn't measure how much income exists in a household. It measures the relative distribution of income across all households in an area. So when one area has a higher Gini index than another, nothing can be said about the income levels between the areas. Rather, it would tell you about the distribution of incomes within both areas.
That being understood, what are the regional, state and nation Gini levels over the last decade or so?
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