(Bloomberg News) The gap between the rich and poor in the U.S. has been concentrated most heavily across a large swath of the South and was least apparent in the Midwest, according to a Census Bureau report.

Six of the 10 counties with the highest income disparity were in Texas, Louisiana, Georgia and South Carolina, all states with Republican governors who usually back the party's presidential candidates.

The report, covering the years 2006-2010, highlights the paradox of the wealth gap as a political issue between voters in so-called red states that tend to vote Republican and blue states that lean Democratic. A 2007 study found that while inequality is more evident in poor states such as Mississippi, voters there largely favor Republican candidates. In wealthier states, they're more likely to back the other major party.

Still, the gap was also pronounced in large urban areas such as New York County, or Manhattan, which had the highest level of income disparity of any major population center in the U.S. and was third overall. The inequality wasn't as evident in less-populous areas such as Loving County, Texas, and fast-growing suburbs like Kendall County, Illinois, near Chicago.

The bureau said income inequality has risen 18% since 1967, with half the growth occurring during the 1980s. It climbed every year between 1998 and 2006 before dropping the following year, and has been rising since.
The nation's three most-populous counties-Los Angeles County; Cook County, Illinois; and Harris County, Texas-were also among the highest urban areas in income inequality.