Some interesting reading over at Freakonomics, with Justin Wolfers, Alex Tabarrok and the US Census Bureau.
Still, income inequality was less pronounced in 1988 Soviet Union, with 70% of the population's income between 75 and 200 rubles per month. I'm not in front of Bloomberg right now, but using the 30-to-1 current FX rate and factoring in the 1000-for-1 redenomination back in 1993, this is $2 to $6 per month, which can't be right. I'll have to check on that, although, given the new job this year, blogging has been difficult.
My thesis is that wealthy nations have high income inequalities and impoverished nations don't.