One way to measure inequality is the GINI index which would be 0.00 for a completely equal country and 1.00 for a country where a Bill Gates earned everything. The index is described at:
http://en.wikipedia.org/wiki/Gini_coefficient
The major international GINI index numbers converted from 0.458 to 45.8 etc (See http://en.wikipedia.org/wiki/List_of_countries_by_income_equality) are using the CIA Year Book numbers for 2009. Note the US is between Iran and Russia in its inequality, well short of South Africa, the most unequal of major countries but much more unequal than many European countries:
- South Africa 65.0
- Chile52.1
- Brazil 51.9
- Mexico 51.7
- Argentina 45.8
- Iran 44.5
- USA 45.0
- Russia 42.0
- China 41.5
- Israel 39.2
- Japan 37.2
- India 36.8
- UK 34.0
- France 32.7
- Canada 32.1
- Italy 32.0
- South Korea 31.4
- Australia 30.5
- Germany 27.0
- Finland 26.8
- Norway 25.0
- Sweden 23.0
Here are some historical trends in GINI since 1945 on a slightly different basis
