Found the top graph via Paul Krugman’s blog. It is from a paper by Larry Bartels, professor of politics and public affairs at Princeton University.
{Click on the image to take a closer look}

I found a second graph in the same paper, showing the income inequality year to year (the 80/20 ratio measures the income inequality by dividing the income earned by someone at the 80th percentile by someone at the 20th percentile). Additionally, Bartels has highlighted the years Democrats and Republicans held the White House. Like a number of graphs on my site, you can see the increase in income inequality since the early 70s.
{Click on the image to take a closer look}

Data in the graphs are calculated from the Historical Income Inequality Tables compiled by the U.S. Census Bureau.
Addendum
5/2/08 Fix my definition of 80/20 income ratio
Technorati Tags: income, United States, inequality, Bartels
Popularity: 3% [?]
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Here is my fifth entry in my series on US Cities. Using 2000 Census data I have mapped % of people living in poverty in the Seattle metropolitan area. you can find the original interactive map at Social Explorer Choose “Poverty” from the second drop down, then select the magnifying glass to zoom in on Seattle.
{Click on the image to take a closer look}

For reference I am including a Google map of Seattle. You can use this map just like the regular Google map and close the white message box.
Popularity: 7% [?]
This is my fourth entry in my series on US Cities. Using 2000 Census data I have mapped % of people living in poverty in the San Francisco-Oakland metropolitan area. If you would like to see the original interactive map go to Social Explorer and choose “Poverty” from the second drop down, then select the magnifying glass to zoom in on San Francisco-Oakland.
{Click on the image to take a closer look}

For reference I am including a Google map of San Francisco-Oakland. You can use this map just like the regular Google map and close the white message box.
View Larger Map
See also:
United States Poverty Map
Technorati Tags: income distribution, US income distribution, inequality, income inequality, income map, poverty, San Francisco, Oakland
Popularity: 7% [?]
Another entry in my series on US Cities. Using 2000 Census data I have mapped % of people living in poverty in Minneapolis-St. Paul’s metropolitan area. The choice was inspired by a Visualizing Economics mention in the Star Tribune. If you would like to see the original interactive map go to Social Explorer and choose “Poverty” from the second drop down, then select the magnifying glass to zoom in on the city.
{Click on the image to take a closer look}

For reference I am including a Google map of the Minneapolis-St. Paul area. You can use this map just like the regular Google map and close the white message box.
Popularity: 5% [?]
Another entry in my series on US Cities. Using 2000 Census data I have mapped % of people living in poverty in Houston’s metropolitan area. If you would like to see the original interactive map go to Social Explorer and choose “Poverty” from the second drop down, then select the magnifying glass to zoom in on Houston.
{Click on the image to take a closer look}

For reference I am including a Google map of Houston, TX. You can use this map just like the regular Google map and close the white message box.
Popularity: 7% [?]