A recent Chicago Fed working paper, Wealth inequality: data and models (WP 2005-10), summarises key facts about wealth distribution in the United States, and what economic models have been able to explain so far. The authors, Marco Cagetti from the University of Virginia and Mariacristina De Nardi from the Chicago Fed, find that wealth in the US "is highly concentrated and very unequally distributed: the richest 1% hold one third of the total wealth in the economy". As to recent trends:
Inequality increased again in the 1980s. Wolf argues that while wealth inequality fell during the 1970s, it rose sharply after 1979, with a dramatic increase over the 1980s, to the level of in the 1990s. The trend in the 1990s is much less clear. The decade saw a stockmarket boom and the rise of some large internet fortunes, as well as increased income concentration.
Compared with other OECD countries (for which data is available) the US is the most unequal:
..the United States exhibits the highest degree of wealth concentration, with the largest shares of total wealth in the hand of the richest percentiles of the wealth distribution. The lowest values are found in, among others, Australia, Italy, Japan and Sweden, and intermediate values in Canada, France and the United Kingdom.
No real surprises - but a useful overview.