The latest available information about the income of taxpayers in each of the nation's 3,140 counties is available on TRAC's IRS Web Site. Included is information about the adjusted gross income, income from dividends and the number of dependents claimed. The data allow the comparison of any county with the others in its state and in the nation as a whole. Special tables list the 50 top and 50 bottom counties.

At $109,661, the taxpayers in Fairfield County, Connecticut reported the highest average gross adjusted income in the United States. This average was nearly six times the $18,481 reported in Hayes County, Nebraska, the lowest in the country.

The five counties reporting the highest average gross adjusted income in 2005 were each located in a different state; three in the east, and two in the west. In 2004, however, the top four counties were all in the east, with three of the top four counties in one state, New Jersey.

After Fairfield County in Connecticut, the next four wealthiest counties were Teton County, Wyoming ($108,171), Goochland County, Virginia ($104,476), Marin County, California ($101,503) and Hunterdon County, New Jersey ($100,922).

The exemptions claimed by a taxpayer is an indicator of the number of children in a household. This means a county claiming comparatively few exemptions is a place with a relatively large number of small families and a county with lots of exemptions is a place with a comparatively large number of large families.

The five counties with the fewest exemptions in the United States were New York County, New York and Arlington County, Virginia (both with 161 per 100 returns), Alexandria City, Virginia (162 per 100 returns), San Francisco County, California (164 per 100 returns) and Pitkin County, Colorado (165 per 100 returns).

Three counties from Utah, and one each from Idaho and Texas were in the top five for the number of exemptions claimed per 100 tax returns in 2005. They were Franklin County, Idaho (289 per 100 returns), Sanpete County, Utah (288 per 100 returns), Juab County, Utah (287 per 100 returns), and Maverick County, Texas and Millard County, Utah (both with 286 per 100 returns).

The difference in wages and salaries between the poorest and the richest counties widened from the prior year. In 2004, the lowest was Petroleum County, Montana ($13,179) and the highest was Hunterdon County, New Jersey ($75,012). In 2005, the lowest was Petroleum County, Montana ($12,592) and the highest was Somerset County, New Jersey ($78,238). This difference has increased by six percent, from $61,833 in 2004 up to $65,646 in 2005.

(See top and bottom 50 county listings.)