File talk:Theil USCounties.png

I think that this is not the Theil Index, but the respective areas contribution TO the Theil Index for the United States. The US is treated as the "Universe" with the income and population shares (the two components of the Theil Index) grouped by location. The Theil Index is always positive. However, contributions to the Theil Index are not (cf. University of Texas Intuitive Explanation of the Theil Index)